diff -r 000000000000 -r 6474c204b198 content/canvas/src/WebGLExtensionDrawBuffers.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/canvas/src/WebGLExtensionDrawBuffers.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 4; 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 "WebGLExtensions.h"
+#include "mozilla/dom/WebGLRenderingContextBinding.h"
+#include "WebGLTexture.h"
+#include "WebGLRenderbuffer.h"
+#include "WebGLFramebuffer.h"
+#include "GLContext.h"
+
+#include <algorithm>
+
+using namespace mozilla;
+using namespace gl;
+
+WebGLExtensionDrawBuffers::WebGLExtensionDrawBuffers(WebGLContext* context)
+    : WebGLExtensionBase(context)
+{
+    GLint maxColorAttachments = 0;
+    GLint maxDrawBuffers = 0;
+
+    gl::GLContext* gl = context->GL();
+
+    context->MakeContextCurrent();
+
+    gl->fGetIntegerv(LOCAL_GL_MAX_COLOR_ATTACHMENTS, &maxColorAttachments);
+    gl->fGetIntegerv(LOCAL_GL_MAX_DRAW_BUFFERS, &maxDrawBuffers);
+
+    // WEBGL_draw_buffers specifications don't give a maximal value reachable by MAX_COLOR_ATTACHMENTS.
+    maxColorAttachments = std::min(maxColorAttachments, GLint(WebGLContext::sMaxColorAttachments));
+
+    if (context->MinCapabilityMode())
+    {
+        maxColorAttachments = std::min(maxColorAttachments, GLint(sMinColorAttachments));
+    }
+
+    // WEBGL_draw_buffers specifications request MAX_COLOR_ATTACHMENTS >= MAX_DRAW_BUFFERS.
+    maxDrawBuffers = std::min(maxDrawBuffers, GLint(maxColorAttachments));
+
+    context->mGLMaxColorAttachments = maxColorAttachments;
+    context->mGLMaxDrawBuffers = maxDrawBuffers;
+}
+
+WebGLExtensionDrawBuffers::~WebGLExtensionDrawBuffers()
+{
+}
+
+void WebGLExtensionDrawBuffers::DrawBuffersWEBGL(const dom::Sequence<GLenum>& buffers)
+{
+    if (mIsLost)
+        return mContext->ErrorInvalidOperation("drawBuffersWEBGL: Extension is lost.");
+
+    mContext->DrawBuffers(buffers);
+}
+
+bool WebGLExtensionDrawBuffers::IsSupported(const WebGLContext* context)
+{
+    gl::GLContext * gl = context->GL();
+
+    if (!gl->IsSupported(GLFeature::draw_buffers)) {
+        return false;
+    }
+
+    GLint supportedColorAttachments = 0;
+    GLint supportedDrawBuffers = 0;
+
+    context->MakeContextCurrent();
+
+    gl->fGetIntegerv(LOCAL_GL_MAX_COLOR_ATTACHMENTS, &supportedColorAttachments);
+    gl->fGetIntegerv(LOCAL_GL_MAX_COLOR_ATTACHMENTS, &supportedDrawBuffers);
+
+    if (size_t(supportedColorAttachments) < sMinColorAttachments){
+        // WEBGL_draw_buffers specifications request for 4 color attachments at least.
+        return false;
+    }
+
+    if (size_t(supportedDrawBuffers) < sMinDrawBuffers){
+        return false;
+    }
+
+    return true;
+}
+
+IMPL_WEBGL_EXTENSION_GOOP(WebGLExtensionDrawBuffers)