Expose if we are using swiftshader via WebGraphicsContext3DProvider.

third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 21 matching lines @@
 #define Canvas2DImageBufferSurface_h
 
 #include "platform/graphics/Canvas2DLayerBridge.h"
 #include "platform/graphics/ImageBufferSurface.h"
 
 namespace blink {
 
 // This shim necessary because ImageBufferSurfaces are not allowed to be RefCounted
 class Canvas2DImageBufferSurface final : public ImageBufferSurface {
 public:
-    Canvas2DImageBufferSurface(const IntSize& size, int msaaSampleCount, OpacityMode opacityMode, Canvas2DLayerBridge::AccelerationMode accelerationMode)
+    Canvas2DImageBufferSurface(std::unique_ptr<WebGraphicsContext3DProvider> contextProvider, const IntSize& size, int msaaSampleCount, OpacityMode opacityMode, Canvas2DLayerBridge::AccelerationMode accelerationMode)
         : ImageBufferSurface(size, opacityMode)
-        , m_layerBridge(Canvas2DLayerBridge::create(size, msaaSampleCount, opacityMode, accelerationMode))
+        , m_layerBridge(adoptRef(new Canvas2DLayerBridge(std::move(contextProvider), size, msaaSampleCount, opacityMode, accelerationMode)))
     {
         init();
     }
 
     Canvas2DImageBufferSurface(PassRefPtr<Canvas2DLayerBridge> bridge, const IntSize& size)
         : ImageBufferSurface(size, bridge->opacityMode())
         , m_layerBridge(std::move(bridge))
     {
         init();
     }
 
-    void init()
-    {
-        clear();
-        if (isValid())
-            m_layerBridge->flush();
-    }
-
     ~Canvas2DImageBufferSurface() override
     {
-        if (m_layerBridge)
-            m_layerBridge->beginDestruction();
+        m_layerBridge->beginDestruction();
     }
 
     // ImageBufferSurface implementation
     void finalizeFrame(const FloatRect &dirtyRect) override { m_layerBridge->finalizeFrame(dirtyRect); }
     void willOverwriteCanvas() override { m_layerBridge->willOverwriteCanvas(); }
     SkCanvas* canvas() override { return m_layerBridge->canvas(); }
     void disableDeferral(DisableDeferralReason reason) override { m_layerBridge->disableDeferral(reason); }
-    bool isValid() const override { return m_layerBridge && m_layerBridge->checkSurfaceValid(); }
+    bool isValid() const override { return m_layerBridge->checkSurfaceValid(); }
     bool restore() override { return m_layerBridge->restoreSurface(); }
     WebLayer* layer() const override { return m_layerBridge->layer(); }
     bool isAccelerated() const override { return m_layerBridge->isAccelerated(); }
     void setFilterQuality(SkFilterQuality filterQuality) override { m_layerBridge->setFilterQuality(filterQuality); }
     void setIsHidden(bool hidden) override { m_layerBridge->setIsHidden(hidden); }
     void setImageBuffer(ImageBuffer* imageBuffer) override { m_layerBridge->setImageBuffer(imageBuffer); }
     void didDraw(const FloatRect& rect) override { m_layerBridge->didDraw(rect); }
     void flush(FlushReason) override { m_layerBridge->flush(); }
     void flushGpu(FlushReason) override { m_layerBridge->flushGpu(); }
     void prepareSurfaceForPaintingIfNeeded() override { m_layerBridge->prepareSurfaceForPaintingIfNeeded(); }
     bool writePixels(const SkImageInfo& origInfo, const void* pixels, size_t rowBytes, int x, int y) override { return m_layerBridge->writePixels(origInfo, pixels, rowBytes, x, y); }
 
     PassRefPtr<SkImage> newImageSnapshot(AccelerationHint hint, SnapshotReason reason) override { return m_layerBridge->newImageSnapshot(hint, reason); }
+
 private:
+    void init()
+    {
+        clear();
+        if (isValid())
+            m_layerBridge->flush();
+    }
+
     RefPtr<Canvas2DLayerBridge> m_layerBridge;
 };
 
 } // namespace blink
 
 #endif