Expose if we are using swiftshader via WebGraphicsContext3DProvider.

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

Index: third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h
diff --git a/third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h b/third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h
index f95a07d355333b6aefb4f5963c3a98c28efdf9fb..7785f3b013bd72ada2cc7b2c63dd1ded89afbdd5 100644
--- a/third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h
+++ b/third_party/WebKit/Source/platform/graphics/Canvas2DImageBufferSurface.h
@@ -39,9 +39,9 @@ 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();
     }
@@ -53,17 +53,9 @@ public:
         init();
     }
 
-    void init()
-    {
-        clear();
-        if (isValid())
-            m_layerBridge->flush();
-    }
-
     ~Canvas2DImageBufferSurface() override
     {
-        if (m_layerBridge)
-            m_layerBridge->beginDestruction();
+        m_layerBridge->beginDestruction();
     }
 
     // ImageBufferSurface implementation
@@ -71,7 +63,7 @@ public:
     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(); }
@@ -85,7 +77,15 @@ public:
     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;
 };