diff -r 000000000000 -r 6474c204b198 mobile/android/base/toolbar/CanvasDelegate.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/toolbar/CanvasDelegate.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,76 @@
+/* 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/. */
+
+package org.mozilla.gecko.toolbar;
+
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.Path;
+import android.graphics.PorterDuff.Mode;
+import android.graphics.PorterDuffXfermode;
+import android.graphics.Shader;
+import android.os.Build;
+
+class CanvasDelegate {
+    Paint mPaint;
+    PorterDuffXfermode mMode;
+    DrawManager mDrawManager;
+
+    // DrawManager would do a default draw of the background.
+    static interface DrawManager {
+        public void defaultDraw(Canvas cavas);
+    }
+
+    CanvasDelegate(DrawManager drawManager, Mode mode) {
+        mDrawManager = drawManager;
+
+        // DST_IN masks, DST_OUT clips.
+        mMode = new PorterDuffXfermode(mode);
+
+        mPaint = new Paint();
+        mPaint.setAntiAlias(true);
+        mPaint.setColor(0xFFFF0000);
+        mPaint.setStrokeWidth(0.0f);
+    }
+
+    void draw(Canvas canvas, Path path, int width, int height) {
+        // Save the canvas. All PorterDuff operations should be done in a offscreen bitmap.
+        int count = canvas.saveLayer(0, 0, width, height, null,
+                                     Canvas.MATRIX_SAVE_FLAG |
+                                     Canvas.CLIP_SAVE_FLAG |
+                                     Canvas.HAS_ALPHA_LAYER_SAVE_FLAG |
+                                     Canvas.FULL_COLOR_LAYER_SAVE_FLAG |
+                                     Canvas.CLIP_TO_LAYER_SAVE_FLAG);
+
+        // Do a default draw.
+        mDrawManager.defaultDraw(canvas);
+
+        if (path != null && !path.isEmpty()) {
+            // ICS added double-buffering, which made it easier for drawing the Path directly over the DST.
+            // In pre-ICS, drawPath() doesn't seem to use ARGB_8888 mode for performance, hence transparency is not preserved.
+            if (Build.VERSION.SDK_INT >= 14) {
+                mPaint.setXfermode(mMode);
+                canvas.drawPath(path, mPaint);
+            } else {
+                // Allocate a bitmap and draw the masking/clipping path.
+                Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+                (new Canvas(bitmap)).drawPath(path, mPaint);
+
+                mPaint.setXfermode(mMode);
+                canvas.drawBitmap(bitmap, 0, 0, mPaint);
+                bitmap.recycle();
+
+                mPaint.setXfermode(null);
+            }
+        }
+
+        // Restore the canvas.
+        canvas.restoreToCount(count);
+    }
+
+    void setShader(Shader shader) {
+        mPaint.setShader(shader);
+    }
+}