Make 2D canvas smarter about chosing whether or not to use GPU acceleration

Source/platform/graphics/Canvas2DLayerBridge.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 33 matching lines @@
 namespace blink {
 
 class Canvas2DLayerBridgeTest;
 class ImageBuffer;
 class WebGraphicsContext3D;
 class WebGraphicsContext3DProvider;
 
 class PLATFORM_EXPORT Canvas2DLayerBridge : public WebExternalTextureLayerClient, public RefCounted<Canvas2DLayerBridge> {
     WTF_MAKE_NONCOPYABLE(Canvas2DLayerBridge);
 public:
-    static PassRefPtr<Canvas2DLayerBridge> create(const IntSize&, OpacityMode, int msaaSampleCount);
+    enum AccelerationMode {
+        DisableAcceleration,
+        EnableAcceleration,
+        ForceAcceleration,

[Stephen White, 2015/09/15 20:43:58]

Please rename ForceAcceleration -> ForceAccelerationForTesting.

+    };
+
+    static PassRefPtr<Canvas2DLayerBridge> create(const IntSize&, int msaaSampleCount, OpacityMode, AccelerationMode);
 
     ~Canvas2DLayerBridge() override;
 
     // WebExternalTextureLayerClient implementation.
     bool prepareMailbox(WebExternalTextureMailbox*, WebExternalBitmap*) override;
     void mailboxReleased(const WebExternalTextureMailbox&, bool lostResource) override;
 
     // ImageBufferSurface implementation
     void finalizeFrame(const FloatRect &dirtyRect);
     void willWritePixels();
     void willOverwriteAllPixels();
     void willOverwriteCanvas();
     SkCanvas* canvas();
     void disableDeferral();
     bool checkSurfaceValid();
     bool restoreSurface();
     WebLayer* layer() const;
-    bool isAccelerated() const { return true; }
+    bool isAccelerated() const;
     void setFilterQuality(SkFilterQuality);
     void setIsHidden(bool);
     void setImageBuffer(ImageBuffer*);
     void didDraw(const FloatRect&);
     bool writePixels(const SkImageInfo&, const void* pixels, size_t rowBytes, int x, int y);
     void flush();
     void flushGpu();
-
+    void prepareSurfaceForPaintingIfNeeded();
     void limitPendingFrames();
     bool isHidden() { return m_isHidden; }
 
     void beginDestruction();
 
-    PassRefPtr<SkImage> newImageSnapshot();
+    PassRefPtr<SkImage> newImageSnapshot(AccelerationHint);
 
 private:
-    Canvas2DLayerBridge(PassOwnPtr<WebGraphicsContext3DProvider>, PassRefPtr<SkSurface>, int, OpacityMode);
+    Canvas2DLayerBridge(PassOwnPtr<WebGraphicsContext3DProvider>, const IntSize&, int msaaSampleCount, OpacityMode, AccelerationMode);
     void setRateLimitingEnabled(bool);
     WebGraphicsContext3D* context();
     void startRecording();
     void skipQueuedDrawCommands();
     void flushRecordingOnly();
+    SkSurface* surface(AccelerationHint = PreferAcceleration);

[Stephen White, 2015/09/15 20:43:58]

<bikeshed> Prefer a name that indicates that this is not just an accessor.
getOrCreateSurface(), or ensureSurface(), or something. </bikeshed>

+    bool shouldAccelerate(AccelerationHint) const;
 
     OwnPtr<SkPictureRecorder> m_recorder;
     RefPtr<SkSurface> m_surface;
     int m_initialSurfaceSaveCount;
     OwnPtr<WebExternalTextureLayer> m_layer;
     OwnPtr<WebGraphicsContext3DProvider> m_contextProvider;
     ImageBuffer* m_imageBuffer;
     int m_msaaSampleCount;
     size_t m_bytesAllocated;
     bool m_haveRecordedDrawCommands;
@@ skipping 19 matching lines @@
     uint32_t m_lastImageId;
 
     enum {
         // We should normally not have more that two active mailboxes at a time,
         // but sometime we may have three due to the async nature of mailbox handling.
         MaxActiveMailboxes = 3,
     };
 
     Deque<MailboxInfo, MaxActiveMailboxes> m_mailboxes;
     GLenum m_lastFilter;
+    AccelerationMode m_accelerationMode;
     OpacityMode m_opacityMode;
     IntSize m_size;
     int m_recordingPixelCount;
 };
 
 } // namespace blink
 
 #endif