Implement image-rendering:pixelated for accelerated 2D canvases.

Source/platform/graphics/Canvas2DLayerBridge.h

Index: Source/platform/graphics/Canvas2DLayerBridge.h
diff --git a/Source/platform/graphics/Canvas2DLayerBridge.h b/Source/platform/graphics/Canvas2DLayerBridge.h
index 897d3aacf50085dec5c8ebc3f59990607cac459a..eabb7f1882215de62f947fffb0edcd8be8329d9e 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.h
+++ b/Source/platform/graphics/Canvas2DLayerBridge.h
@@ -75,6 +75,7 @@ public:
     WebLayer* layer() const;
     Platform3DObject getBackingTexture();
     bool isAccelerated() const { return true; }
+    void setFilterLevel(SkPaint::FilterLevel);
     void setIsHidden(bool);
     void setImageBuffer(ImageBuffer* imageBuffer) { m_imageBuffer = imageBuffer; }
 
@@ -110,6 +111,7 @@ protected:
     int m_framesSinceMailboxRelease;
     bool m_destructionInProgress;
     bool m_rateLimitingEnabled;
+    SkPaint::FilterLevel m_filterLevel;
     bool m_isHidden;
 
     friend class WTF::DoublyLinkedListNode<Canvas2DLayerBridge>;
@@ -135,6 +137,7 @@ protected:
     };
 
     Deque<MailboxInfo, MaxActiveMailboxes> m_mailboxes;
+    GLenum m_lastFilter;
     OpacityMode m_opacityMode;
 };