Refactoring Canvas2DLayerBridge to make it easier to write unit tests

Source/core/platform/graphics/ImageBuffer.cpp

Index: Source/core/platform/graphics/ImageBuffer.cpp
diff --git a/Source/core/platform/graphics/ImageBuffer.cpp b/Source/core/platform/graphics/ImageBuffer.cpp
index 86fde9637bf93805800850150773d2a31cea747d..8f25602d03fca50efbd63a44f757e9f46158e772 100644
--- a/Source/core/platform/graphics/ImageBuffer.cpp
+++ b/Source/core/platform/graphics/ImageBuffer.cpp
@@ -61,13 +61,40 @@ using namespace std;
 
 namespace WebCore {
 
+namespace {
+
+class AcceleratedLayerHelper : public Canvas2DLayerBridge::Helper {
+public:
+    virtual PassRefPtr<GraphicsContext3D> getContext() OVERRIDE
+    {
+        return SharedGraphicsContext3D::get();
+    }
+
+    virtual SkSurface* createSurface(GraphicsContext3D* context3D, const IntSize& size) OVERRIDE
+    {
+        ASSERT(!context3D->webContext()->isContextLost());
+        GrContext* gr = context3D->grContext();
+        if (!gr)
+            return 0;
+        gr->resetContext();
+        SkImage::Info info;
+        info.fWidth = size.width();
+        info.fHeight = size.height();
+        info.fColorType = SkImage::kPMColor_ColorType;
+        info.fAlphaType = SkImage::kPremul_AlphaType;
+        return SkSurface::NewRenderTarget(gr, info);
+    }
+};
+
+} // unnamed namespace
+
 static SkCanvas* createAcceleratedCanvas(const IntSize& size, OwnPtr<Canvas2DLayerBridge>* outLayerBridge, OpacityMode opacityMode)
 {
-    RefPtr<GraphicsContext3D> context3D = SharedGraphicsContext3D::get();
-    if (!context3D)
+    OwnPtr<AcceleratedLayerHelper> helper = adoptPtr(new AcceleratedLayerHelper);
+    if (!helper->getContext())
         return 0;
     Canvas2DLayerBridge::OpacityMode bridgeOpacityMode = opacityMode == Opaque ? Canvas2DLayerBridge::Opaque : Canvas2DLayerBridge::NonOpaque;
-    *outLayerBridge = Canvas2DLayerBridge::create(context3D.release(), size, bridgeOpacityMode);
+    *outLayerBridge = Canvas2DLayerBridge::create(helper.release(), size, bridgeOpacityMode);
     // If canvas buffer allocation failed, debug build will have asserted
     // For release builds, we must verify whether the device has a render target
     return (*outLayerBridge) ? (*outLayerBridge)->getCanvas() : 0;