diff -r 000000000000 -r 6474c204b198 content/canvas/src/WebGLContextValidate.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/canvas/src/WebGLContextValidate.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,1866 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebGLContext.h"
+#include "WebGLBuffer.h"
+#include "WebGLVertexAttribData.h"
+#include "WebGLShader.h"
+#include "WebGLProgram.h"
+#include "WebGLUniformLocation.h"
+#include "WebGLFramebuffer.h"
+#include "WebGLRenderbuffer.h"
+#include "WebGLTexture.h"
+#include "WebGLVertexArray.h"
+#include "GLContext.h"
+#include "CanvasUtils.h"
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+
+#include "jsfriendapi.h"
+
+#include "angle/ShaderLang.h"
+
+#include <algorithm>
+
+#include "mozilla/Services.h"
+#include "nsIObserverService.h"
+
+using namespace mozilla;
+
+/**
+ * Return the block size for format.
+ */
+static void
+BlockSizeFor(GLenum format, GLint* blockWidth, GLint* blockHeight)
+{
+    MOZ_ASSERT(blockWidth && blockHeight);
+
+    switch (format) {
+    case LOCAL_GL_ATC_RGB:
+    case LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA:
+    case LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA:
+    case LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+        if (blockWidth)
+            *blockWidth = 4;
+        if (blockHeight)
+            *blockHeight = 4;
+        break;
+
+    case LOCAL_GL_ETC1_RGB8_OES:
+        // 4x4 blocks, but no 4-multiple requirement.
+    default:
+        break;
+    }
+}
+
+/**
+ * Return the displayable name for the texture function that is the
+ * source for validation.
+ */
+static const char*
+InfoFrom(WebGLTexImageFunc func)
+{
+    // TODO: Account for dimensions (WebGL 2)
+    switch (func) {
+    case WebGLTexImageFunc::TexImage:        return "texImage2D";
+    case WebGLTexImageFunc::TexSubImage:     return "texSubImage2D";
+    case WebGLTexImageFunc::CopyTexImage:    return "copyTexImage2D";
+    case WebGLTexImageFunc::CopyTexSubImage: return "copyTexSubImage2D";
+    case WebGLTexImageFunc::CompTexImage:    return "compressedTexImage2D";
+    case WebGLTexImageFunc::CompTexSubImage: return "compressedTexSubImage2D";
+    default:
+        MOZ_ASSERT(false, "Missing case for WebGLTexImageSource");
+        return "(error)";
+    }
+}
+
+/**
+ * Return displayable name for GLenum.
+ * This version is like gl::GLenumToStr but with out the GL_ prefix to
+ * keep consistency with how errors are reported from WebGL.
+ */
+static const char*
+NameFrom(GLenum glenum)
+{
+    switch (glenum) {
+#define XX(x) case LOCAL_GL_##x: return #x
+        XX(ALPHA);
+        XX(ATC_RGB);
+        XX(ATC_RGBA_EXPLICIT_ALPHA);
+        XX(ATC_RGBA_INTERPOLATED_ALPHA);
+        XX(COMPRESSED_RGBA_PVRTC_2BPPV1);
+        XX(COMPRESSED_RGBA_PVRTC_4BPPV1);
+        XX(COMPRESSED_RGBA_S3TC_DXT1_EXT);
+        XX(COMPRESSED_RGBA_S3TC_DXT3_EXT);
+        XX(COMPRESSED_RGBA_S3TC_DXT5_EXT);
+        XX(COMPRESSED_RGB_PVRTC_2BPPV1);
+        XX(COMPRESSED_RGB_PVRTC_4BPPV1);
+        XX(COMPRESSED_RGB_S3TC_DXT1_EXT);
+        XX(DEPTH_COMPONENT);
+        XX(DEPTH_COMPONENT16);
+        XX(DEPTH_COMPONENT32);
+        XX(DEPTH_STENCIL);
+        XX(DEPTH24_STENCIL8);
+        XX(ETC1_RGB8_OES);
+        XX(FLOAT);
+        XX(HALF_FLOAT);
+        XX(LUMINANCE);
+        XX(LUMINANCE_ALPHA);
+        XX(RGB);
+        XX(RGB16F);
+        XX(RGB32F);
+        XX(RGBA);
+        XX(RGBA16F);
+        XX(RGBA32F);
+        XX(SRGB);
+        XX(SRGB_ALPHA);
+        XX(TEXTURE_2D);
+        XX(TEXTURE_3D);
+        XX(TEXTURE_CUBE_MAP);
+        XX(TEXTURE_CUBE_MAP_NEGATIVE_X);
+        XX(TEXTURE_CUBE_MAP_NEGATIVE_Y);
+        XX(TEXTURE_CUBE_MAP_NEGATIVE_Z);
+        XX(TEXTURE_CUBE_MAP_POSITIVE_X);
+        XX(TEXTURE_CUBE_MAP_POSITIVE_Y);
+        XX(TEXTURE_CUBE_MAP_POSITIVE_Z);
+        XX(UNSIGNED_BYTE);
+        XX(UNSIGNED_INT);
+        XX(UNSIGNED_INT_24_8);
+        XX(UNSIGNED_SHORT);
+        XX(UNSIGNED_SHORT_4_4_4_4);
+        XX(UNSIGNED_SHORT_5_5_5_1);
+        XX(UNSIGNED_SHORT_5_6_5);
+#undef XX
+    }
+
+    return nullptr;
+}
+
+/**
+ * Same as ErrorInvalidEnum but uses NameFrom to print displayable
+ * name for \a glenum.
+ */
+static void
+ErrorInvalidEnumWithName(WebGLContext* ctx, const char* msg, GLenum glenum, WebGLTexImageFunc func)
+{
+    const char* name = NameFrom(glenum);
+    if (name)
+        ctx->ErrorInvalidEnum("%s: %s %s", InfoFrom(func), msg, name);
+    else
+        ctx->ErrorInvalidEnum("%s: %s 0x%04X", InfoFrom(func), msg, glenum);
+}
+
+/**
+ * Same as ErrorInvalidOperation but uses NameFrom to print displayable
+ * name for \a glenum.
+ */
+static void
+ErrorInvalidOperationWithName(WebGLContext* ctx, const char* msg, GLenum glenum,
+                              WebGLTexImageFunc func)
+{
+    const char* name = NameFrom(glenum);
+    if (name)
+        ctx->ErrorInvalidOperation("%s: %s %s", InfoFrom(func), msg, name);
+    else
+        ctx->ErrorInvalidOperation("%s: %s 0x%04X", InfoFrom(func), msg, glenum);
+}
+
+/**
+ * Return true if the format is valid for source calls.
+ */
+static bool
+IsAllowedFromSource(GLenum format, WebGLTexImageFunc func)
+{
+    switch (format) {
+    case LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1:
+        return (func == WebGLTexImageFunc::CompTexImage ||
+                func == WebGLTexImageFunc::CompTexSubImage);
+
+    case LOCAL_GL_ATC_RGB:
+    case LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA:
+    case LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA:
+    case LOCAL_GL_ETC1_RGB8_OES:
+        return func == WebGLTexImageFunc::CompTexImage;
+    }
+
+    return true;
+}
+
+/**
+ * Returns true if func is a CopyTexImage variant.
+ */
+static bool
+IsCopyFunc(WebGLTexImageFunc func)
+{
+    return (func == WebGLTexImageFunc::CopyTexImage ||
+            func == WebGLTexImageFunc::CopyTexSubImage);
+}
+
+/**
+ * Returns true if func is a SubImage variant.
+ */
+static bool
+IsSubFunc(WebGLTexImageFunc func)
+{
+    return (func == WebGLTexImageFunc::TexSubImage ||
+            func == WebGLTexImageFunc::CopyTexSubImage ||
+            func == WebGLTexImageFunc::CompTexSubImage);
+}
+
+/**
+ * returns true is target is a texture cube map target.
+ */
+static bool
+IsTexImageCubemapTarget(GLenum target)
+{
+    return (target >= LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X &&
+            target <= LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z);
+}
+
+/*
+ * Pull data out of the program, post-linking
+ */
+bool
+WebGLProgram::UpdateInfo()
+{
+    mIdentifierMap = nullptr;
+    mIdentifierReverseMap = nullptr;
+    mUniformInfoMap = nullptr;
+
+    mAttribMaxNameLength = 0;
+
+    for (size_t i = 0; i < mAttachedShaders.Length(); i++)
+        mAttribMaxNameLength = std::max(mAttribMaxNameLength, mAttachedShaders[i]->mAttribMaxNameLength);
+
+    GLint attribCount;
+    mContext->gl->fGetProgramiv(mGLName, LOCAL_GL_ACTIVE_ATTRIBUTES, &attribCount);
+
+    if (!mAttribsInUse.SetLength(mContext->mGLMaxVertexAttribs)) {
+        mContext->ErrorOutOfMemory("updateInfo: out of memory to allocate %d attribs", mContext->mGLMaxVertexAttribs);
+        return false;
+    }
+
+    for (size_t i = 0; i < mAttribsInUse.Length(); i++)
+        mAttribsInUse[i] = false;
+
+    nsAutoArrayPtr<char> nameBuf(new char[mAttribMaxNameLength]);
+
+    for (int i = 0; i < attribCount; ++i) {
+        GLint attrnamelen;
+        GLint attrsize;
+        GLenum attrtype;
+        mContext->gl->fGetActiveAttrib(mGLName, i, mAttribMaxNameLength, &attrnamelen, &attrsize, &attrtype, nameBuf);
+        if (attrnamelen > 0) {
+            GLint loc = mContext->gl->fGetAttribLocation(mGLName, nameBuf);
+            MOZ_ASSERT(loc >= 0, "major oops in managing the attributes of a WebGL program");
+            if (loc < mContext->mGLMaxVertexAttribs) {
+                mAttribsInUse[loc] = true;
+            } else {
+                mContext->GenerateWarning("program exceeds MAX_VERTEX_ATTRIBS");
+                return false;
+            }
+        }
+    }
+
+    if (!mUniformInfoMap) {
+        mUniformInfoMap = new CStringToUniformInfoMap;
+        for (size_t i = 0; i < mAttachedShaders.Length(); i++) {
+            for (size_t j = 0; j < mAttachedShaders[i]->mUniforms.Length(); j++) {
+                const WebGLMappedIdentifier& uniform = mAttachedShaders[i]->mUniforms[j];
+                const WebGLUniformInfo& info = mAttachedShaders[i]->mUniformInfos[j];
+                mUniformInfoMap->Put(uniform.mapped, info);
+            }
+        }
+    }
+
+    mActiveAttribMap.clear();
+
+    GLint numActiveAttrs = 0;
+    mContext->gl->fGetProgramiv(mGLName, LOCAL_GL_ACTIVE_ATTRIBUTES, &numActiveAttrs);
+
+    // Spec says the maximum attrib name length is 256 chars, so this is
+    // sufficient to hold any attrib name.
+    char attrName[257];
+
+    GLint dummySize;
+    GLenum dummyType;
+    for (GLint i = 0; i < numActiveAttrs; i++) {
+        mContext->gl->fGetActiveAttrib(mGLName, i, 257, nullptr, &dummySize,
+                                       &dummyType, attrName);
+        GLint attrLoc = mContext->gl->fGetAttribLocation(mGLName, attrName);
+        MOZ_ASSERT(attrLoc >= 0);
+        mActiveAttribMap.insert(std::make_pair(attrLoc, nsCString(attrName)));
+    }
+
+    return true;
+}
+
+/**
+ * Return the simple base format for a given internal format.
+ *
+ * \return the corresponding \u base internal format (GL_ALPHA, GL_LUMINANCE,
+ * GL_LUMINANCE_ALPHA, GL_RGB, GL_RGBA), or GL_NONE if invalid enum.
+ */
+GLenum
+WebGLContext::BaseTexFormat(GLenum internalFormat) const
+{
+    if (internalFormat == LOCAL_GL_ALPHA ||
+        internalFormat == LOCAL_GL_LUMINANCE ||
+        internalFormat == LOCAL_GL_LUMINANCE_ALPHA ||
+        internalFormat == LOCAL_GL_RGB ||
+        internalFormat == LOCAL_GL_RGBA)
+    {
+        return internalFormat;
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::EXT_sRGB)) {
+        if (internalFormat == LOCAL_GL_SRGB)
+            return LOCAL_GL_RGB;
+
+        if (internalFormat == LOCAL_GL_SRGB_ALPHA)
+            return LOCAL_GL_RGBA;
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_atc)) {
+        if (internalFormat == LOCAL_GL_ATC_RGB)
+            return LOCAL_GL_RGB;
+
+        if (internalFormat == LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA ||
+            internalFormat == LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA)
+        {
+            return LOCAL_GL_RGBA;
+        }
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_etc1)) {
+        if (internalFormat == LOCAL_GL_ETC1_RGB8_OES)
+            return LOCAL_GL_RGB;
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_pvrtc)) {
+        if (internalFormat == LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1 ||
+            internalFormat == LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1)
+        {
+            return LOCAL_GL_RGB;
+        }
+
+        if (internalFormat == LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1 ||
+            internalFormat == LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1)
+        {
+            return LOCAL_GL_RGBA;
+        }
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_s3tc)) {
+        if (internalFormat == LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT)
+            return LOCAL_GL_RGB;
+
+        if (internalFormat == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT ||
+            internalFormat == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT ||
+            internalFormat == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT)
+        {
+            return LOCAL_GL_RGBA;
+        }
+    }
+
+    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_depth_texture)) {
+        if (internalFormat == LOCAL_GL_DEPTH_COMPONENT ||
+            internalFormat == LOCAL_GL_DEPTH_COMPONENT16 ||
+            internalFormat == LOCAL_GL_DEPTH_COMPONENT32)
+        {
+            return LOCAL_GL_DEPTH_COMPONENT;
+        }
+
+        if (internalFormat == LOCAL_GL_DEPTH_STENCIL ||
+            internalFormat == LOCAL_GL_DEPTH24_STENCIL8)
+        {
+            return LOCAL_GL_DEPTH_STENCIL;
+        }
+    }
+
+    MOZ_ASSERT(false, "Unhandled internalFormat");
+    return LOCAL_GL_NONE;
+}
+
+bool WebGLContext::ValidateBlendEquationEnum(GLenum mode, const char *info)
+{
+    switch (mode) {
+        case LOCAL_GL_FUNC_ADD:
+        case LOCAL_GL_FUNC_SUBTRACT:
+        case LOCAL_GL_FUNC_REVERSE_SUBTRACT:
+            return true;
+        case LOCAL_GL_MIN:
+        case LOCAL_GL_MAX:
+            if (IsWebGL2()) {
+                // http://www.opengl.org/registry/specs/EXT/blend_minmax.txt
+                return true;
+            }
+            break;
+        default:
+            break;
+    }
+
+    ErrorInvalidEnumInfo(info, mode);
+    return false;
+}
+
+bool WebGLContext::ValidateBlendFuncDstEnum(GLenum factor, const char *info)
+{
+    switch (factor) {
+        case LOCAL_GL_ZERO:
+        case LOCAL_GL_ONE:
+        case LOCAL_GL_SRC_COLOR:
+        case LOCAL_GL_ONE_MINUS_SRC_COLOR:
+        case LOCAL_GL_DST_COLOR:
+        case LOCAL_GL_ONE_MINUS_DST_COLOR:
+        case LOCAL_GL_SRC_ALPHA:
+        case LOCAL_GL_ONE_MINUS_SRC_ALPHA:
+        case LOCAL_GL_DST_ALPHA:
+        case LOCAL_GL_ONE_MINUS_DST_ALPHA:
+        case LOCAL_GL_CONSTANT_COLOR:
+        case LOCAL_GL_ONE_MINUS_CONSTANT_COLOR:
+        case LOCAL_GL_CONSTANT_ALPHA:
+        case LOCAL_GL_ONE_MINUS_CONSTANT_ALPHA:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, factor);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateBlendFuncSrcEnum(GLenum factor, const char *info)
+{
+    if (factor == LOCAL_GL_SRC_ALPHA_SATURATE)
+        return true;
+    else
+        return ValidateBlendFuncDstEnum(factor, info);
+}
+
+bool WebGLContext::ValidateBlendFuncEnumsCompatibility(GLenum sfactor, GLenum dfactor, const char *info)
+{
+    bool sfactorIsConstantColor = sfactor == LOCAL_GL_CONSTANT_COLOR ||
+                                    sfactor == LOCAL_GL_ONE_MINUS_CONSTANT_COLOR;
+    bool sfactorIsConstantAlpha = sfactor == LOCAL_GL_CONSTANT_ALPHA ||
+                                    sfactor == LOCAL_GL_ONE_MINUS_CONSTANT_ALPHA;
+    bool dfactorIsConstantColor = dfactor == LOCAL_GL_CONSTANT_COLOR ||
+                                    dfactor == LOCAL_GL_ONE_MINUS_CONSTANT_COLOR;
+    bool dfactorIsConstantAlpha = dfactor == LOCAL_GL_CONSTANT_ALPHA ||
+                                    dfactor == LOCAL_GL_ONE_MINUS_CONSTANT_ALPHA;
+    if ( (sfactorIsConstantColor && dfactorIsConstantAlpha) ||
+         (dfactorIsConstantColor && sfactorIsConstantAlpha) ) {
+        ErrorInvalidOperation("%s are mutually incompatible, see section 6.8 in the WebGL 1.0 spec", info);
+        return false;
+    } else {
+        return true;
+    }
+}
+
+bool WebGLContext::ValidateTextureTargetEnum(GLenum target, const char *info)
+{
+    switch (target) {
+        case LOCAL_GL_TEXTURE_2D:
+        case LOCAL_GL_TEXTURE_CUBE_MAP:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, target);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateComparisonEnum(GLenum target, const char *info)
+{
+    switch (target) {
+        case LOCAL_GL_NEVER:
+        case LOCAL_GL_LESS:
+        case LOCAL_GL_LEQUAL:
+        case LOCAL_GL_GREATER:
+        case LOCAL_GL_GEQUAL:
+        case LOCAL_GL_EQUAL:
+        case LOCAL_GL_NOTEQUAL:
+        case LOCAL_GL_ALWAYS:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, target);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateStencilOpEnum(GLenum action, const char *info)
+{
+    switch (action) {
+        case LOCAL_GL_KEEP:
+        case LOCAL_GL_ZERO:
+        case LOCAL_GL_REPLACE:
+        case LOCAL_GL_INCR:
+        case LOCAL_GL_INCR_WRAP:
+        case LOCAL_GL_DECR:
+        case LOCAL_GL_DECR_WRAP:
+        case LOCAL_GL_INVERT:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, action);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateFaceEnum(GLenum face, const char *info)
+{
+    switch (face) {
+        case LOCAL_GL_FRONT:
+        case LOCAL_GL_BACK:
+        case LOCAL_GL_FRONT_AND_BACK:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, face);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateDrawModeEnum(GLenum mode, const char *info)
+{
+    switch (mode) {
+        case LOCAL_GL_TRIANGLES:
+        case LOCAL_GL_TRIANGLE_STRIP:
+        case LOCAL_GL_TRIANGLE_FAN:
+        case LOCAL_GL_POINTS:
+        case LOCAL_GL_LINE_STRIP:
+        case LOCAL_GL_LINE_LOOP:
+        case LOCAL_GL_LINES:
+            return true;
+        default:
+            ErrorInvalidEnumInfo(info, mode);
+            return false;
+    }
+}
+
+bool WebGLContext::ValidateGLSLVariableName(const nsAString& name, const char *info)
+{
+    if (name.IsEmpty())
+        return false;
+
+    const uint32_t maxSize = 256;
+    if (name.Length() > maxSize) {
+        ErrorInvalidValue("%s: identifier is %d characters long, exceeds the maximum allowed length of %d characters",
+                          info, name.Length(), maxSize);
+        return false;
+    }
+
+    if (!ValidateGLSLString(name, info)) {
+        return false;
+    }
+
+    nsString prefix1 = NS_LITERAL_STRING("webgl_");
+    nsString prefix2 = NS_LITERAL_STRING("_webgl_");
+
+    if (Substring(name, 0, prefix1.Length()).Equals(prefix1) ||
+        Substring(name, 0, prefix2.Length()).Equals(prefix2))
+    {
+        ErrorInvalidOperation("%s: string contains a reserved GLSL prefix", info);
+        return false;
+    }
+
+    return true;
+}
+
+bool WebGLContext::ValidateGLSLString(const nsAString& string, const char *info)
+{
+    for (uint32_t i = 0; i < string.Length(); ++i) {
+        if (!ValidateGLSLCharacter(string.CharAt(i))) {
+             ErrorInvalidValue("%s: string contains the illegal character '%d'", info, string.CharAt(i));
+             return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * Return true if format is a valid texture image format for source,
+ * taking into account enabled WebGL extensions.
+ */
+bool
+WebGLContext::ValidateTexImageFormat(GLenum format, WebGLTexImageFunc func)
+{
+    /* Core WebGL texture formats */
+    if (format == LOCAL_GL_ALPHA ||
+        format == LOCAL_GL_RGB ||
+        format == LOCAL_GL_RGBA ||
+        format == LOCAL_GL_LUMINANCE ||
+        format == LOCAL_GL_LUMINANCE_ALPHA)
+    {
+        return true;
+    }
+
+    /* Only core formats are valid for CopyTex(Sub)?Image */
+    // TODO: Revisit this once color_buffer_(half_)?float lands
+    if (IsCopyFunc(func)) {
+        ErrorInvalidEnumWithName(this, "invalid format", format, func);
+        return false;
+    }
+
+    /* WEBGL_depth_texture added formats */
+    if (format == LOCAL_GL_DEPTH_COMPONENT ||
+        format == LOCAL_GL_DEPTH_STENCIL)
+    {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::WEBGL_depth_texture);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need WEBGL_depth_texture enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+    /* EXT_sRGB added formats */
+    if (format == LOCAL_GL_SRGB ||
+        format == LOCAL_GL_SRGB_ALPHA)
+    {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::EXT_sRGB);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need EXT_sRGB enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+    /* WEBGL_compressed_texture_atc added formats */
+    if (format == LOCAL_GL_ATC_RGB ||
+        format == LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA ||
+        format == LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA)
+    {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_atc);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need WEBGL_compressed_texture_atc enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+    // WEBGL_compressed_texture_etc1
+    if (format == LOCAL_GL_ETC1_RGB8_OES) {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_etc1);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need WEBGL_compressed_texture_etc1 enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+
+    if (format == LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1 ||
+        format == LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1 ||
+        format == LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1 ||
+        format == LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1)
+    {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_pvrtc);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need WEBGL_compressed_texture_pvrtc enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+
+    if (format == LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT ||
+        format == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT ||
+        format == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT ||
+        format == LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT)
+    {
+        bool validFormat = IsExtensionEnabled(WebGLExtensionID::WEBGL_compressed_texture_s3tc);
+        if (!validFormat)
+            ErrorInvalidEnum("%s: invalid format %s: need WEBGL_compressed_texture_s3tc enabled",
+                             InfoFrom(func), NameFrom(format));
+        return validFormat;
+    }
+
+    ErrorInvalidEnumWithName(this, "invalid format", format, func);
+
+    return false;
+}
+
+/**
+ * Check if the given texture target is valid for TexImage.
+ */
+bool
+WebGLContext::ValidateTexImageTarget(GLuint dims, GLenum target, WebGLTexImageFunc func)
+{
+    switch (dims) {
+    case 2:
+        if (target == LOCAL_GL_TEXTURE_2D ||
+            IsTexImageCubemapTarget(target))
+        {
+            return true;
+        }
+
+        ErrorInvalidEnumWithName(this, "invalid target", target, func);
+        return false;
+
+    default:
+        MOZ_ASSERT(false, "ValidateTexImageTarget: Invalid dims");
+    }
+
+    return false;
+}
+
+/**
+ * Return true if type is a valid texture image type for source,
+ * taking into account enabled WebGL extensions.
+ */
+bool
+WebGLContext::ValidateTexImageType(GLenum type, WebGLTexImageFunc func)
+{
+    /* Core WebGL texture types */
+    if (type == LOCAL_GL_UNSIGNED_BYTE ||
+        type == LOCAL_GL_UNSIGNED_SHORT_5_6_5 ||
+        type == LOCAL_GL_UNSIGNED_SHORT_4_4_4_4 ||
+        type == LOCAL_GL_UNSIGNED_SHORT_5_5_5_1)
+    {
+        return true;
+    }
+
+    /* OES_texture_float added types */
+    if (type == LOCAL_GL_FLOAT) {
+        bool validType = IsExtensionEnabled(WebGLExtensionID::OES_texture_float);
+        if (!validType)
+            ErrorInvalidEnum("%s: invalid type %s: need OES_texture_float enabled",
+                             InfoFrom(func), NameFrom(type));
+        return validType;
+    }
+
+    /* OES_texture_half_float add types */
+    if (type == LOCAL_GL_HALF_FLOAT_OES) {
+        bool validType = IsExtensionEnabled(WebGLExtensionID::OES_texture_half_float);
+        if (!validType)
+            ErrorInvalidEnum("%s: invalid type %s: need OES_texture_half_float enabled",
+                             InfoFrom(func), NameFrom(type));
+        return validType;
+    }
+
+    /* WEBGL_depth_texture added types */
+    if (type == LOCAL_GL_UNSIGNED_SHORT ||
+        type == LOCAL_GL_UNSIGNED_INT ||
+        type == LOCAL_GL_UNSIGNED_INT_24_8)
+    {
+        bool validType = IsExtensionEnabled(WebGLExtensionID::WEBGL_depth_texture);
+        if (!validType)
+            ErrorInvalidEnum("%s: invalid type %s: need WEBGL_depth_texture enabled",
+                             InfoFrom(func), NameFrom(type));
+        return validType;
+    }
+
+    ErrorInvalidEnumWithName(this, "invalid type", type, func);
+    return false;
+}
+
+/**
+ * Validate texture image sizing extra constraints for
+ * CompressedTex(Sub)?Image.
+ */
+// TODO: WebGL 2
+bool
+WebGLContext::ValidateCompTexImageSize(GLenum target, GLint level, GLenum format,
+                                       GLint xoffset, GLint yoffset,
+                                       GLsizei width, GLsizei height,
+                                       GLsizei levelWidth, GLsizei levelHeight,
+                                       WebGLTexImageFunc func)
+{
+    // Negative parameters must already have been handled above
+    MOZ_ASSERT(xoffset >= 0 && yoffset >= 0 &&
+               width >= 0 && height >= 0);
+
+    if (xoffset + width > (GLint) levelWidth) {
+        ErrorInvalidValue("%s: xoffset + width must be <= levelWidth", InfoFrom(func));
+        return false;
+    }
+
+    if (yoffset + height > (GLint) levelHeight) {
+        ErrorInvalidValue("%s: yoffset + height must be <= levelHeight", InfoFrom(func));
+        return false;
+    }
+
+    GLint blockWidth = 1;
+    GLint blockHeight = 1;
+    BlockSizeFor(format, &blockWidth, &blockHeight);
+
+    /* If blockWidth || blockHeight != 1, then the compressed format
+     * had block-based constraints to be checked. (For example, PVRTC is compressed but
+     * isn't a block-based format)
+     */
+    if (blockWidth != 1 || blockHeight != 1) {
+        /* offsets must be multiple of block size */
+        if (xoffset % blockWidth != 0) {
+            ErrorInvalidOperation("%s: xoffset must be multiple of %d",
+                                  InfoFrom(func), blockWidth);
+            return false;
+        }
+
+        if (yoffset % blockHeight != 0) {
+            ErrorInvalidOperation("%s: yoffset must be multiple of %d",
+                                  InfoFrom(func), blockHeight);
+            return false;
+        }
+
+        /* The size must be a multiple of blockWidth and blockHeight,
+         * or must be using offset+size that exactly hits the edge.
+         * Important for small mipmap levels.
+         */
+        /* https://www.khronos.org/registry/webgl/extensions/WEBGL_compressed_texture_s3tc/
+         * "When level equals zero width and height must be a multiple of 4. When
+         *  level is greater than 0 width and height must be 0, 1, 2 or a multiple of 4.
+         *  If they are not an INVALID_OPERATION error is generated."
+         */
+        if (level == 0) {
+            if (width % blockWidth != 0) {
+                ErrorInvalidOperation("%s: width of level 0 must be multple of %d",
+                                      InfoFrom(func), blockWidth);
+                return false;
+            }
+
+            if (height % blockHeight != 0) {
+                ErrorInvalidOperation("%s: height of level 0 must be multipel of %d",
+                                      InfoFrom(func), blockHeight);
+                return false;
+            }
+        }
+        else if (level > 0) {
+            if (width % blockWidth != 0 && width > 2) {
+                ErrorInvalidOperation("%s: width of level %d must be multiple"
+                                      " of %d or 0, 1, 2",
+                                      InfoFrom(func), level, blockWidth);
+                return false;
+            }
+
+            if (height % blockHeight != 0 && height > 2) {
+                ErrorInvalidOperation("%s: height of level %d must be multiple"
+                                      " of %d or 0, 1, 2",
+                                      InfoFrom(func), level, blockHeight);
+                return false;
+            }
+        }
+
+        if (IsSubFunc(func)) {
+            if ((xoffset % blockWidth) != 0) {
+                ErrorInvalidOperation("%s: xoffset must be multiple of %d",
+                                      InfoFrom(func), blockWidth);
+                return false;
+            }
+
+            if (yoffset % blockHeight != 0) {
+                ErrorInvalidOperation("%s: yoffset must be multiple of %d",
+                                      InfoFrom(func), blockHeight);
+                return false;
+            }
+        }
+    }
+
+    switch (format) {
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1:
+        if (!is_pot_assuming_nonnegative(width) ||
+            !is_pot_assuming_nonnegative(height))
+        {
+            ErrorInvalidValue("%s: width and height must be powers of two",
+                              InfoFrom(func));
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * Return true if the enough data is present to satisfy compressed
+ * texture format constraints.
+ */
+bool
+WebGLContext::ValidateCompTexImageDataSize(GLint level, GLenum format,
+                                           GLsizei width, GLsizei height,
+                                           uint32_t byteLength, WebGLTexImageFunc func)
+{
+    // negative width and height must already have been handled above
+    MOZ_ASSERT(width >= 0 && height >= 0);
+
+    CheckedUint32 required_byteLength = 0;
+
+    switch (format) {
+        case LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+        case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+        case LOCAL_GL_ATC_RGB:
+        case LOCAL_GL_ETC1_RGB8_OES:
+        {
+            required_byteLength = ((CheckedUint32(width) + 3) / 4) * ((CheckedUint32(height) + 3) / 4) * 8;
+            break;
+        }
+        case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+        case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+        case LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA:
+        case LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA:
+        {
+            required_byteLength = ((CheckedUint32(width) + 3) / 4) * ((CheckedUint32(height) + 3) / 4) * 16;
+            break;
+        }
+        case LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1:
+        case LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1:
+        {
+            required_byteLength = CheckedUint32(std::max(width, 8)) * CheckedUint32(std::max(height, 8)) / 2;
+            break;
+        }
+        case LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1:
+        case LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1:
+        {
+            required_byteLength = CheckedUint32(std::max(width, 16)) * CheckedUint32(std::max(height, 8)) / 4;
+            break;
+        }
+    }
+
+    if (!required_byteLength.isValid() || required_byteLength.value() != byteLength) {
+        ErrorInvalidValue("%s: data size does not match dimensions", InfoFrom(func));
+        return false;
+    }
+
+    return true;
+}
+
+/**
+ * Validate the width, height, and depth of a texture image, \return
+ * true is valid, false otherwise.
+ * Used by all the (Compressed|Copy)?Tex(Sub)?Image functions.
+ * Target and level must have been validated before calling.
+ */
+bool
+WebGLContext::ValidateTexImageSize(GLenum target, GLint level,
+                                   GLint width, GLint height, GLint depth,
+                                   WebGLTexImageFunc func)
+{
+    MOZ_ASSERT(level >= 0, "level should already be validated");
+
+    /* Bug 966630: maxTextureSize >> level runs into "undefined"
+     * behaviour depending on ISA. For example, on Intel shifts
+     * amounts are mod 64 (in 64-bit mode on 64-bit dest) and mod 32
+     * otherwise. This means 16384 >> 0x10000001 == 8192 which isn't
+     * what would be expected. Make the required behaviour explicit by
+     * clamping to a shift of 31 bits if level is greater than that
+     * ammount. This will give 0 that if (!maxAllowedSize) is
+     * expecting.
+     */
+
+    if (level > 31)
+        level = 31;
+
+    const GLuint maxTexImageSize = MaxTextureSizeForTarget(target) >> level;
+    const bool isCubemapTarget = IsTexImageCubemapTarget(target);
+    const bool isSub = IsSubFunc(func);
+
+    if (!isSub && isCubemapTarget && (width != height)) {
+        /* GL ES Version 2.0.25 - 3.7.1 Texture Image Specification
+         *   "When the target parameter to TexImage2D is one of the
+         *   six cube map two-dimensional image targets, the error
+         *   INVALID_VALUE is generated if the width and height
+         *   parameters are not equal."
+         */
+        ErrorInvalidValue("%s: for cube map, width must equal height", InfoFrom(func));
+        return false;
+    }
+
+    if (target == LOCAL_GL_TEXTURE_2D || isCubemapTarget)
+    {
+        /* GL ES Version 2.0.25 - 3.7.1 Texture Image Specification
+         *   "If wt and ht are the specified image width and height,
+         *   and if either wt or ht are less than zero, then the error
+         *   INVALID_VALUE is generated."
+         */
+        if (width < 0) {
+            ErrorInvalidValue("%s: width must be >= 0", InfoFrom(func));
+            return false;
+        }
+
+        if (height < 0) {
+            ErrorInvalidValue("%s: height must be >= 0", InfoFrom(func));
+            return false;
+        }
+
+        /* GL ES Version 2.0.25 - 3.7.1 Texture Image Specification
+         *   "The maximum allowable width and height of a
+         *   two-dimensional texture image must be at least 2**(k−lod)
+         *   for image arrays of level zero through k, where k is the
+         *   log base 2 of MAX_TEXTURE_SIZE. and lod is the
+         *   level-of-detail of the image array. It may be zero for
+         *   image arrays of any level-of-detail greater than k. The
+         *   error INVALID_VALUE is generated if the specified image
+         *   is too large to be stored under any conditions.
+         */
+        if (width > (int) maxTexImageSize) {
+            ErrorInvalidValue("%s: the maximum width for level %d is %u",
+                              InfoFrom(func), level, maxTexImageSize);
+            return false;
+        }
+
+        if (height > (int) maxTexImageSize) {
+            ErrorInvalidValue("%s: tex maximum height for level %d is %u",
+                              InfoFrom(func), level, maxTexImageSize);
+            return false;
+        }
+
+        /* GL ES Version 2.0.25 - 3.7.1 Texture Image Specification
+         *   "If level is greater than zero, and either width or
+         *   height is not a power-of-two, the error INVALID_VALUE is
+         *   generated."
+         */
+        if (level > 0) {
+            if (!is_pot_assuming_nonnegative(width)) {
+                ErrorInvalidValue("%s: level >= 0, width of %d must be a power of two.",
+                                  InfoFrom(func), width);
+                return false;
+            }
+
+            if (!is_pot_assuming_nonnegative(height)) {
+                ErrorInvalidValue("%s: level >= 0, height of %d must be a power of two.",
+                                  InfoFrom(func), height);
+                return false;
+            }
+        }
+    }
+
+    // TODO: WebGL 2
+    if (target == LOCAL_GL_TEXTURE_3D) {
+        if (depth < 0) {
+            ErrorInvalidValue("%s: depth must be >= 0", InfoFrom(func));
+            return false;
+        }
+
+        if (!is_pot_assuming_nonnegative(depth)) {
+            ErrorInvalidValue("%s: level >= 0, depth of %d must be a power of two.",
+                              InfoFrom(func), depth);
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * Validate texture image sizing for Tex(Sub)?Image variants.
+ */
+// TODO: WebGL 2. Update this to handle 3D textures.
+bool
+WebGLContext::ValidateTexSubImageSize(GLint xoffset, GLint yoffset, GLint /*zoffset*/,
+                                      GLsizei width, GLsizei height, GLsizei /*depth*/,
+                                      GLsizei baseWidth, GLsizei baseHeight, GLsizei /*baseDepth*/,
+                                      WebGLTexImageFunc func)
+{
+    /* GL ES Version 2.0.25 - 3.7.1 Texture Image Specification
+     *   "Taking wt and ht to be the specified width and height of the
+     *   texture array, and taking x, y, w, and h to be the xoffset,
+     *   yoffset, width, and height argument values, any of the
+     *   following relationships generates the error INVALID_VALUE:
+     *       x < 0
+     *       x + w > wt
+     *       y < 0
+     *       y + h > ht"
+     */
+
+    if (xoffset < 0) {
+        ErrorInvalidValue("%s: xoffset must be >= 0", InfoFrom(func));
+        return false;
+    }
+
+    if (yoffset < 0) {
+        ErrorInvalidValue("%s: yoffset must be >= 0", InfoFrom(func));
+        return false;
+    }
+
+    if (!CanvasUtils::CheckSaneSubrectSize(xoffset, yoffset, width, height, baseWidth, baseHeight)) {
+        ErrorInvalidValue("%s: subtexture rectangle out-of-bounds", InfoFrom(func));
+        return false;
+    }
+
+    return true;
+}
+
+/**
+ * Return the bits per texel for format & type combination.
+ * Assumes that format & type are a valid combination as checked with
+ * ValidateTexImageFormatAndType().
+ */
+uint32_t
+WebGLContext::GetBitsPerTexel(GLenum format, GLenum type)
+{
+    // If there is no defined format or type, we're not taking up any memory
+    if (!format || !type) {
+        return 0;
+    }
+
+    /* Known fixed-sized types */
+    if (type == LOCAL_GL_UNSIGNED_SHORT_4_4_4_4 ||
+        type == LOCAL_GL_UNSIGNED_SHORT_5_5_5_1 ||
+        type == LOCAL_GL_UNSIGNED_SHORT_5_6_5)
+    {
+        return 16;
+    }
+
+    if (type == LOCAL_GL_UNSIGNED_INT_24_8)
+        return 32;
+
+    int bitsPerComponent = 0;
+    switch (type) {
+    case LOCAL_GL_UNSIGNED_BYTE:
+        bitsPerComponent = 8;
+        break;
+
+    case LOCAL_GL_HALF_FLOAT:
+    case LOCAL_GL_HALF_FLOAT_OES:
+    case LOCAL_GL_UNSIGNED_SHORT:
+        bitsPerComponent = 16;
+        break;
+
+    case LOCAL_GL_FLOAT:
+    case LOCAL_GL_UNSIGNED_INT:
+        bitsPerComponent = 32;
+        break;
+
+    default:
+        MOZ_ASSERT(false, "Unhandled type.");
+        break;
+    }
+
+    switch (format) {
+        // Uncompressed formats
+    case LOCAL_GL_ALPHA:
+    case LOCAL_GL_LUMINANCE:
+    case LOCAL_GL_DEPTH_COMPONENT:
+    case LOCAL_GL_DEPTH_STENCIL:
+        return 1 * bitsPerComponent;
+
+    case LOCAL_GL_LUMINANCE_ALPHA:
+        return 2 * bitsPerComponent;
+
+    case LOCAL_GL_RGB:
+    case LOCAL_GL_RGB32F:
+    case LOCAL_GL_SRGB_EXT:
+        return 3 * bitsPerComponent;
+
+    case LOCAL_GL_RGBA:
+    case LOCAL_GL_RGBA32F:
+    case LOCAL_GL_SRGB_ALPHA_EXT:
+        return 4 * bitsPerComponent;
+
+        // Compressed formats
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1:
+        return 2;
+
+    case LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+    case LOCAL_GL_ATC_RGB:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1:
+    case LOCAL_GL_ETC1_RGB8_OES:
+        return 4;
+
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+    case LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA:
+    case LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA:
+        return 8;
+
+    default:
+        break;
+    }
+
+    MOZ_ASSERT(false, "Unhandled format+type combo.");
+    return 0;
+}
+
+/**
+ * Perform validation of format/type combinations for TexImage variants.
+ * Returns true if the format/type is a valid combination, false otherwise.
+ */
+bool
+WebGLContext::ValidateTexImageFormatAndType(GLenum format, GLenum type, WebGLTexImageFunc func)
+{
+    if (!ValidateTexImageFormat(format, func) ||
+        !ValidateTexImageType(type, func))
+    {
+        return false;
+    }
+
+    bool validCombo = false;
+
+    switch (format) {
+    case LOCAL_GL_ALPHA:
+    case LOCAL_GL_LUMINANCE:
+    case LOCAL_GL_LUMINANCE_ALPHA:
+        validCombo = (type == LOCAL_GL_UNSIGNED_BYTE ||
+                      type == LOCAL_GL_HALF_FLOAT ||
+                      type == LOCAL_GL_HALF_FLOAT_OES ||
+                      type == LOCAL_GL_FLOAT);
+        break;
+
+    case LOCAL_GL_RGB:
+    case LOCAL_GL_SRGB:
+        validCombo = (type == LOCAL_GL_UNSIGNED_BYTE ||
+                      type == LOCAL_GL_UNSIGNED_SHORT_5_6_5 ||
+                      type == LOCAL_GL_HALF_FLOAT ||
+                      type == LOCAL_GL_HALF_FLOAT_OES ||
+                      type == LOCAL_GL_FLOAT);
+        break;
+
+    case LOCAL_GL_RGBA:
+    case LOCAL_GL_SRGB_ALPHA:
+        validCombo = (type == LOCAL_GL_UNSIGNED_BYTE ||
+                      type == LOCAL_GL_UNSIGNED_SHORT_4_4_4_4 ||
+                      type == LOCAL_GL_UNSIGNED_SHORT_5_5_5_1 ||
+                      type == LOCAL_GL_HALF_FLOAT ||
+                      type == LOCAL_GL_HALF_FLOAT_OES ||
+                      type == LOCAL_GL_FLOAT);
+        break;
+
+    case LOCAL_GL_DEPTH_COMPONENT:
+        validCombo = (type == LOCAL_GL_UNSIGNED_SHORT ||
+                      type == LOCAL_GL_UNSIGNED_INT);
+        break;
+
+    case LOCAL_GL_DEPTH_STENCIL:
+        validCombo = (type == LOCAL_GL_UNSIGNED_INT_24_8);
+        break;
+
+    case LOCAL_GL_ATC_RGB:
+    case LOCAL_GL_ATC_RGBA_EXPLICIT_ALPHA:
+    case LOCAL_GL_ATC_RGBA_INTERPOLATED_ALPHA:
+    case LOCAL_GL_ETC1_RGB8_OES:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGB_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_2BPPV1:
+    case LOCAL_GL_COMPRESSED_RGBA_PVRTC_4BPPV1:
+    case LOCAL_GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
+    case LOCAL_GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+        validCombo = (type == LOCAL_GL_UNSIGNED_BYTE);
+        break;
+
+    default:
+        // Only valid formats should be passed to the switch stmt.
+        MOZ_ASSERT(false, "Unexpected format and type combo. How'd this happen?");
+        validCombo = false;
+        // Fall through to return an InvalidOperations. This will alert us to the
+        // unexpected case that needs fixing in builds without asserts.
+    }
+
+    if (!validCombo)
+        ErrorInvalidOperation("%s: invalid combination of format %s and type %s",
+                              InfoFrom(func), NameFrom(format), NameFrom(type));
+
+    return validCombo;
+}
+
+/**
+ * Return true if format, type and jsArrayType are a valid combination.
+ * Also returns the size for texel of format and type (in bytes) via
+ * \a texelSize.
+ *
+ * It is assumed that type has previously been validated.
+ */
+bool
+WebGLContext::ValidateTexInputData(GLenum type, int jsArrayType, WebGLTexImageFunc func)
+{
+    bool validInput = false;
+    const char invalidTypedArray[] = "%s: invalid typed array type for given texture data type";
+
+    // First, we check for packed types
+    switch (type) {
+    case LOCAL_GL_UNSIGNED_BYTE:
+        validInput = (jsArrayType == -1 || jsArrayType == js::ArrayBufferView::TYPE_UINT8);
+        break;
+
+        // TODO: WebGL spec doesn't allow half floats to specified as UInt16.
+    case LOCAL_GL_HALF_FLOAT:
+    case LOCAL_GL_HALF_FLOAT_OES:
+        validInput = (jsArrayType == -1);
+        break;
+
+    case LOCAL_GL_UNSIGNED_SHORT:
+    case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
+    case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
+    case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
+        validInput = (jsArrayType == -1 || jsArrayType == js::ArrayBufferView::TYPE_UINT16);
+        break;
+
+    case LOCAL_GL_UNSIGNED_INT:
+    case LOCAL_GL_UNSIGNED_INT_24_8:
+        validInput = (jsArrayType == -1 || jsArrayType == js::ArrayBufferView::TYPE_UINT32);
+        break;
+
+    case LOCAL_GL_FLOAT:
+        validInput = (jsArrayType == -1 || jsArrayType == js::ArrayBufferView::TYPE_FLOAT32);
+        break;
+
+    default:
+        break;
+    }
+
+    if (!validInput)
+        ErrorInvalidOperation(invalidTypedArray, InfoFrom(func));
+
+    return validInput;
+}
+
+/**
+ * Test the gl(Copy|Compressed)?Tex[Sub]?Image[23]() parameters for errors.
+ * Verifies each of the parameters against the WebGL standard and enabled extensions.
+ */
+// TODO: Texture dims is here for future expansion in WebGL 2.0
+bool
+WebGLContext::ValidateTexImage(GLuint dims, GLenum target,
+                               GLint level, GLint internalFormat,
+                               GLint xoffset, GLint yoffset, GLint zoffset,
+                               GLint width, GLint height, GLint depth,
+                               GLint border, GLenum format, GLenum type,
+                               WebGLTexImageFunc func)
+{
+    const char* info = InfoFrom(func);
+
+    /* Check target */
+    if (!ValidateTexImageTarget(dims, target, func))
+        return false;
+
+    /* Check level */
+    if (level < 0) {
+        ErrorInvalidValue("%s: level must be >= 0", info);
+        return false;
+    }
+
+    /* Check border */
+    if (border != 0) {
+        ErrorInvalidValue("%s: border must be 0", info);
+        return false;
+    }
+
+    /* Check incoming image format and type */
+    if (!ValidateTexImageFormatAndType(format, type, func))
+        return false;
+
+    /* WebGL and OpenGL ES 2.0 impose additional restrictions on the
+     * combinations of format, internalFormat, and type that can be
+     * used.  Formats and types that require additional extensions
+     * (e.g., GL_FLOAT requires GL_OES_texture_float) are filtered
+     * elsewhere.
+     */
+    if ((GLint) format != internalFormat) {
+        ErrorInvalidOperation("%s: format does not match internalformat", info);
+        return false;
+    }
+
+    /* check internalFormat */
+    // TODO: Not sure if this is a bit of over kill.
+    if (BaseTexFormat(internalFormat) == LOCAL_GL_NONE) {
+        MOZ_ASSERT(false);
+        ErrorInvalidValue("%s:", info);
+        return false;
+    }
+
+    /* Check texture image size */
+    if (!ValidateTexImageSize(target, level, width, height, 0, func))
+        return false;
+
+    /* 5.14.8 Texture objects - WebGL Spec.
+     *   "If an attempt is made to call these functions with no
+     *    WebGLTexture bound (see above), an INVALID_OPERATION error
+     *    is generated."
+     */
+    WebGLTexture* tex = activeBoundTextureForTarget(target);
+    if (!tex) {
+        ErrorInvalidOperation("%s: no texture is bound to target %s",
+                              info, NameFrom(target));
+        return false;
+    }
+
+    if (IsSubFunc(func)) {
+        if (!tex->HasImageInfoAt(target, level)) {
+            ErrorInvalidOperation("%s: no texture image previously defined for target %s at level %d",
+                                  info, NameFrom(target), level);
+            return false;
+        }
+
+        const WebGLTexture::ImageInfo& imageInfo = tex->ImageInfoAt(target, level);
+        if (!ValidateTexSubImageSize(xoffset, yoffset, zoffset,
+                                     width, height, depth,
+                                     imageInfo.Width(), imageInfo.Height(), 0,
+                                     func))
+        {
+            return false;
+        }
+
+        /* Require the format and type to match that of the existing
+         * texture as created
+         */
+        if (imageInfo.WebGLFormat() != format ||
+            imageInfo.WebGLType() != type)
+        {
+            ErrorInvalidOperation("%s: format or type doesn't match the existing texture",
+                                  info);
+            return false;
+        }
+    }
+
+    /* Additional checks for depth textures */
+    if (format == LOCAL_GL_DEPTH_COMPONENT ||
+        format == LOCAL_GL_DEPTH_STENCIL)
+    {
+        if (func == WebGLTexImageFunc::TexSubImage || IsCopyFunc(func)) {
+            ErrorInvalidOperationWithName(this, "called with format/internalformat",
+                                          format, func);
+            return false;
+        }
+
+        if (func == WebGLTexImageFunc::TexImage &&
+            target != LOCAL_GL_TEXTURE_2D)
+        {
+            ErrorInvalidOperation("%s: with format of %s target must be TEXTURE_2D",
+                                  info, NameFrom(format));
+            return false;
+        }
+
+        if (func == WebGLTexImageFunc::TexImage && level != 0) {
+            ErrorInvalidOperation("%s: with format of %s target, level must be 0",
+                                  info, NameFrom(format));
+            return false;
+        }
+    }
+
+    /* Additional checks for compressed textures */
+    if (!IsAllowedFromSource(format, func)) {
+        ErrorInvalidOperation("%s: Invalid format %s for this operation",
+                              info, NameFrom(format));
+        return false;
+    }
+
+    /* Parameters are OK */
+    return true;
+}
+
+bool
+WebGLContext::ValidateUniformLocation(const char* info, WebGLUniformLocation *location_object)
+{
+    if (!ValidateObjectAllowNull(info, location_object))
+        return false;
+    if (!location_object)
+        return false;
+    /* the need to check specifically for !mCurrentProgram here is explained in bug 657556 */
+    if (!mCurrentProgram) {
+        ErrorInvalidOperation("%s: no program is currently bound", info);
+        return false;
+    }
+    if (mCurrentProgram != location_object->Program()) {
+        ErrorInvalidOperation("%s: this uniform location doesn't correspond to the current program", info);
+        return false;
+    }
+    if (mCurrentProgram->Generation() != location_object->ProgramGeneration()) {
+        ErrorInvalidOperation("%s: This uniform location is obsolete since the program has been relinked", info);
+        return false;
+    }
+    return true;
+}
+
+bool
+WebGLContext::ValidateSamplerUniformSetter(const char* info, WebGLUniformLocation *location, GLint value)
+{
+    if (location->Info().type != SH_SAMPLER_2D &&
+        location->Info().type != SH_SAMPLER_CUBE)
+    {
+        return true;
+    }
+
+    if (value >= 0 && value < mGLMaxTextureUnits)
+        return true;
+
+    ErrorInvalidValue("%s: this uniform location is a sampler, but %d is not a valid texture unit",
+                      info, value);
+    return false;
+}
+
+bool
+WebGLContext::ValidateAttribArraySetter(const char* name, uint32_t cnt, uint32_t arrayLength)
+{
+    if (IsContextLost()) {
+        return false;
+    }
+    if (arrayLength < cnt) {
+        ErrorInvalidOperation("%s: array must be >= %d elements", name, cnt);
+        return false;
+    }
+    return true;
+}
+
+bool
+WebGLContext::ValidateUniformArraySetter(const char* name, uint32_t expectedElemSize, WebGLUniformLocation *location_object,
+                                         GLint& location, uint32_t& numElementsToUpload, uint32_t arrayLength)
+{
+    if (IsContextLost())
+        return false;
+    if (!ValidateUniformLocation(name, location_object))
+        return false;
+    location = location_object->Location();
+    uint32_t uniformElemSize = location_object->ElementSize();
+    if (expectedElemSize != uniformElemSize) {
+        ErrorInvalidOperation("%s: this function expected a uniform of element size %d,"
+                              " got a uniform of element size %d", name,
+                              expectedElemSize,
+                              uniformElemSize);
+        return false;
+    }
+    if (arrayLength == 0 ||
+        arrayLength % expectedElemSize)
+    {
+        ErrorInvalidValue("%s: expected an array of length a multiple"
+                          " of %d, got an array of length %d", name,
+                          expectedElemSize,
+                          arrayLength);
+        return false;
+    }
+    const WebGLUniformInfo& info = location_object->Info();
+    if (!info.isArray &&
+        arrayLength != expectedElemSize) {
+        ErrorInvalidOperation("%s: expected an array of length exactly"
+                              " %d (since this uniform is not an array"
+                              " uniform), got an array of length %d", name,
+                              expectedElemSize,
+                              arrayLength);
+        return false;
+    }
+    numElementsToUpload =
+        std::min(info.arraySize, arrayLength / expectedElemSize);
+    return true;
+}
+
+bool
+WebGLContext::ValidateUniformMatrixArraySetter(const char* name, int dim, WebGLUniformLocation *location_object,
+                                              GLint& location, uint32_t& numElementsToUpload, uint32_t arrayLength,
+                                              WebGLboolean aTranspose)
+{
+    uint32_t expectedElemSize = (dim)*(dim);
+    if (IsContextLost())
+        return false;
+    if (!ValidateUniformLocation(name, location_object))
+        return false;
+    location = location_object->Location();
+    uint32_t uniformElemSize = location_object->ElementSize();
+    if (expectedElemSize != uniformElemSize) {
+        ErrorInvalidOperation("%s: this function expected a uniform of element size %d,"
+                              " got a uniform of element size %d", name,
+                              expectedElemSize,
+                              uniformElemSize);
+        return false;
+    }
+    if (arrayLength == 0 ||
+        arrayLength % expectedElemSize)
+    {
+        ErrorInvalidValue("%s: expected an array of length a multiple"
+                          " of %d, got an array of length %d", name,
+                          expectedElemSize,
+                          arrayLength);
+        return false;
+    }
+    const WebGLUniformInfo& info = location_object->Info();
+    if (!info.isArray &&
+        arrayLength != expectedElemSize) {
+        ErrorInvalidOperation("%s: expected an array of length exactly"
+                              " %d (since this uniform is not an array"
+                              " uniform), got an array of length %d", name,
+                              expectedElemSize,
+                              arrayLength);
+        return false;
+    }
+    if (aTranspose) {
+        ErrorInvalidValue("%s: transpose must be FALSE as per the "
+                          "OpenGL ES 2.0 spec", name);
+        return false;
+    }
+    numElementsToUpload =
+        std::min(info.arraySize, arrayLength / (expectedElemSize));
+    return true;
+}
+
+bool
+WebGLContext::ValidateUniformSetter(const char* name, WebGLUniformLocation *location_object, GLint& location)
+{
+    if (IsContextLost())
+        return false;
+    if (!ValidateUniformLocation(name, location_object))
+        return false;
+    location = location_object->Location();
+    return true;
+}
+
+bool WebGLContext::ValidateAttribIndex(GLuint index, const char *info)
+{
+    return mBoundVertexArray->EnsureAttrib(index, info);
+}
+
+bool WebGLContext::ValidateStencilParamsForDrawCall()
+{
+  const char *msg = "%s set different front and back stencil %s. Drawing in this configuration is not allowed.";
+  if (mStencilRefFront != mStencilRefBack) {
+      ErrorInvalidOperation(msg, "stencilFuncSeparate", "reference values");
+      return false;
+  }
+  if (mStencilValueMaskFront != mStencilValueMaskBack) {
+      ErrorInvalidOperation(msg, "stencilFuncSeparate", "value masks");
+      return false;
+  }
+  if (mStencilWriteMaskFront != mStencilWriteMaskBack) {
+      ErrorInvalidOperation(msg, "stencilMaskSeparate", "write masks");
+      return false;
+  }
+  return true;
+}
+
+static inline int32_t floorPOT(int32_t x)
+{
+    MOZ_ASSERT(x > 0);
+    int32_t pot = 1;
+    while (pot < 0x40000000) {
+        if (x < pot*2)
+            break;
+        pot *= 2;
+    }
+    return pot;
+}
+
+bool
+WebGLContext::InitAndValidateGL()
+{
+    if (!gl) return false;
+
+    GLenum error = gl->fGetError();
+    if (error != LOCAL_GL_NO_ERROR) {
+        GenerateWarning("GL error 0x%x occurred during OpenGL context initialization, before WebGL initialization!", error);
+        return false;
+    }
+
+    mMinCapability = Preferences::GetBool("webgl.min_capability_mode", false);
+    mDisableExtensions = Preferences::GetBool("webgl.disable-extensions", false);
+    mLoseContextOnHeapMinimize = Preferences::GetBool("webgl.lose-context-on-heap-minimize", false);
+    mCanLoseContextInForeground = Preferences::GetBool("webgl.can-lose-context-in-foreground", true);
+
+    if (MinCapabilityMode()) {
+      mDisableFragHighP = true;
+    }
+
+    // These are the default values, see 6.2 State tables in the
+    // OpenGL ES 2.0.25 spec.
+    mColorWriteMask[0] = 1;
+    mColorWriteMask[1] = 1;
+    mColorWriteMask[2] = 1;
+    mColorWriteMask[3] = 1;
+    mDepthWriteMask = 1;
+    mColorClearValue[0] = 0.f;
+    mColorClearValue[1] = 0.f;
+    mColorClearValue[2] = 0.f;
+    mColorClearValue[3] = 0.f;
+    mDepthClearValue = 1.f;
+    mStencilClearValue = 0;
+    mStencilRefFront = 0;
+    mStencilRefBack = 0;
+    mStencilValueMaskFront = 0xffffffff;
+    mStencilValueMaskBack  = 0xffffffff;
+    mStencilWriteMaskFront = 0xffffffff;
+    mStencilWriteMaskBack  = 0xffffffff;
+
+    // Bindings, etc.
+    mActiveTexture = 0;
+    mEmitContextLostErrorOnce = true;
+    mWebGLError = LOCAL_GL_NO_ERROR;
+    mUnderlyingGLError = LOCAL_GL_NO_ERROR;
+
+    mBound2DTextures.Clear();
+    mBoundCubeMapTextures.Clear();
+
+    mBoundArrayBuffer = nullptr;
+    mBoundTransformFeedbackBuffer = nullptr;
+    mCurrentProgram = nullptr;
+
+    mBoundFramebuffer = nullptr;
+    mBoundRenderbuffer = nullptr;
+
+    MakeContextCurrent();
+
+    // on desktop OpenGL, we always keep vertex attrib 0 array enabled
+    if (!gl->IsGLES()) {
+        gl->fEnableVertexAttribArray(0);
+    }
+
+    if (MinCapabilityMode()) {
+        mGLMaxVertexAttribs = MINVALUE_GL_MAX_VERTEX_ATTRIBS;
+    } else {
+        gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_ATTRIBS, &mGLMaxVertexAttribs);
+    }
+    if (mGLMaxVertexAttribs < 8) {
+        GenerateWarning("GL_MAX_VERTEX_ATTRIBS: %d is < 8!", mGLMaxVertexAttribs);
+        return false;
+    }
+
+    // Note: GL_MAX_TEXTURE_UNITS is fixed at 4 for most desktop hardware,
+    // even though the hardware supports much more.  The
+    // GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS value is the accurate value.
+    if (MinCapabilityMode()) {
+        mGLMaxTextureUnits = MINVALUE_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS;
+    } else {
+        gl->fGetIntegerv(LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &mGLMaxTextureUnits);
+    }
+    if (mGLMaxTextureUnits < 8) {
+        GenerateWarning("GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS: %d is < 8!", mGLMaxTextureUnits);
+        return false;
+    }
+
+    mBound2DTextures.SetLength(mGLMaxTextureUnits);
+    mBoundCubeMapTextures.SetLength(mGLMaxTextureUnits);
+
+    if (MinCapabilityMode()) {
+        mGLMaxTextureSize = MINVALUE_GL_MAX_TEXTURE_SIZE;
+        mGLMaxCubeMapTextureSize = MINVALUE_GL_MAX_CUBE_MAP_TEXTURE_SIZE;
+        mGLMaxRenderbufferSize = MINVALUE_GL_MAX_RENDERBUFFER_SIZE;
+        mGLMaxTextureImageUnits = MINVALUE_GL_MAX_TEXTURE_IMAGE_UNITS;
+        mGLMaxVertexTextureImageUnits = MINVALUE_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS;
+    } else {
+        gl->fGetIntegerv(LOCAL_GL_MAX_TEXTURE_SIZE, &mGLMaxTextureSize);
+        gl->fGetIntegerv(LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE, &mGLMaxCubeMapTextureSize);
+        gl->fGetIntegerv(LOCAL_GL_MAX_RENDERBUFFER_SIZE, &mGLMaxRenderbufferSize);
+        gl->fGetIntegerv(LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS, &mGLMaxTextureImageUnits);
+        gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS, &mGLMaxVertexTextureImageUnits);
+    }
+
+    mGLMaxTextureSize = floorPOT(mGLMaxTextureSize);
+    mGLMaxRenderbufferSize = floorPOT(mGLMaxRenderbufferSize);
+
+    if (MinCapabilityMode()) {
+        mGLMaxFragmentUniformVectors = MINVALUE_GL_MAX_FRAGMENT_UNIFORM_VECTORS;
+        mGLMaxVertexUniformVectors = MINVALUE_GL_MAX_VERTEX_UNIFORM_VECTORS;
+        mGLMaxVaryingVectors = MINVALUE_GL_MAX_VARYING_VECTORS;
+    } else {
+        if (gl->IsSupported(gl::GLFeature::ES2_compatibility)) {
+            gl->fGetIntegerv(LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS, &mGLMaxFragmentUniformVectors);
+            gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS, &mGLMaxVertexUniformVectors);
+            gl->fGetIntegerv(LOCAL_GL_MAX_VARYING_VECTORS, &mGLMaxVaryingVectors);
+        } else {
+            gl->fGetIntegerv(LOCAL_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &mGLMaxFragmentUniformVectors);
+            mGLMaxFragmentUniformVectors /= 4;
+            gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_UNIFORM_COMPONENTS, &mGLMaxVertexUniformVectors);
+            mGLMaxVertexUniformVectors /= 4;
+
+            // we are now going to try to read GL_MAX_VERTEX_OUTPUT_COMPONENTS and GL_MAX_FRAGMENT_INPUT_COMPONENTS,
+            // however these constants only entered the OpenGL standard at OpenGL 3.2. So we will try reading,
+            // and check OpenGL error for INVALID_ENUM.
+
+            // before we start, we check that no error already occurred, to prevent hiding it in our subsequent error handling
+            error = gl->GetAndClearError();
+            if (error != LOCAL_GL_NO_ERROR) {
+                GenerateWarning("GL error 0x%x occurred during WebGL context initialization!", error);
+                return false;
+            }
+
+            // On the public_webgl list, "problematic GetParameter pnames" thread, the following formula was given:
+            //   mGLMaxVaryingVectors = min (GL_MAX_VERTEX_OUTPUT_COMPONENTS, GL_MAX_FRAGMENT_INPUT_COMPONENTS) / 4
+            GLint maxVertexOutputComponents,
+                  minFragmentInputComponents;
+            gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_OUTPUT_COMPONENTS, &maxVertexOutputComponents);
+            gl->fGetIntegerv(LOCAL_GL_MAX_FRAGMENT_INPUT_COMPONENTS, &minFragmentInputComponents);
+
+            error = gl->GetAndClearError();
+            switch (error) {
+                case LOCAL_GL_NO_ERROR:
+                    mGLMaxVaryingVectors = std::min(maxVertexOutputComponents, minFragmentInputComponents) / 4;
+                    break;
+                case LOCAL_GL_INVALID_ENUM:
+                    mGLMaxVaryingVectors = 16; // = 64/4, 64 is the min value for maxVertexOutputComponents in OpenGL 3.2 spec
+                    break;
+                default:
+                    GenerateWarning("GL error 0x%x occurred during WebGL context initialization!", error);
+                    return false;
+            }
+        }
+    }
+
+    // Always 1 for GLES2
+    mMaxFramebufferColorAttachments = 1;
+
+    if (!gl->IsGLES()) {
+        // gl_PointSize is always available in ES2 GLSL, but has to be
+        // specifically enabled on desktop GLSL.
+        gl->fEnable(LOCAL_GL_VERTEX_PROGRAM_POINT_SIZE);
+
+        // gl_PointCoord is always available in ES2 GLSL and in newer desktop GLSL versions, but apparently
+        // not in OpenGL 2 and apparently not (due to a driver bug) on certain NVIDIA setups. See:
+        //   http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=261472
+        // Note that this used to cause crashes on old ATI drivers... hopefully not a significant
+        // problem anymore. See bug 602183.
+        gl->fEnable(LOCAL_GL_POINT_SPRITE);
+    }
+
+#ifdef XP_MACOSX
+    if (gl->WorkAroundDriverBugs() &&
+        gl->Vendor() == gl::GLVendor::ATI) {
+        // The Mac ATI driver, in all known OSX version up to and including 10.8,
+        // renders points sprites upside-down. Apple bug 11778921
+        gl->fPointParameterf(LOCAL_GL_POINT_SPRITE_COORD_ORIGIN, LOCAL_GL_LOWER_LEFT);
+    }
+#endif
+
+    // Check the shader validator pref
+    NS_ENSURE_TRUE(Preferences::GetRootBranch(), false);
+
+    mShaderValidation =
+        Preferences::GetBool("webgl.shader_validator", mShaderValidation);
+
+    // initialize shader translator
+    if (mShaderValidation) {
+        if (!ShInitialize()) {
+            GenerateWarning("GLSL translator initialization failed!");
+            return false;
+        }
+    }
+
+    // Mesa can only be detected with the GL_VERSION string, of the form "2.1 Mesa 7.11.0"
+    mIsMesa = strstr((const char *)(gl->fGetString(LOCAL_GL_VERSION)), "Mesa");
+
+    // notice that the point of calling GetAndClearError here is not only to check for error,
+    // it is also to reset the error flags so that a subsequent WebGL getError call will give the correct result.
+    error = gl->GetAndClearError();
+    if (error != LOCAL_GL_NO_ERROR) {
+        GenerateWarning("GL error 0x%x occurred during WebGL context initialization!", error);
+        return false;
+    }
+
+    if (IsWebGL2() &&
+        !InitWebGL2())
+    {
+        // Todo: Bug 898404: Only allow WebGL2 on GL>=3.0 on desktop GL.
+        return false;
+    }
+
+    mMemoryPressureObserver
+        = new WebGLMemoryPressureObserver(this);
+    nsCOMPtr<nsIObserverService> observerService
+        = mozilla::services::GetObserverService();
+    if (observerService) {
+        observerService->AddObserver(mMemoryPressureObserver,
+                                     "memory-pressure",
+                                     false);
+    }
+
+    mDefaultVertexArray = new WebGLVertexArray(this);
+    mDefaultVertexArray->mAttribs.SetLength(mGLMaxVertexAttribs);
+    mBoundVertexArray = mDefaultVertexArray;
+
+    return true;
+}