Refactoring ImageBuffer to decouple it from Canvas2DLayerBridge

Source/core/rendering/shapes/Shape.cpp

Index: Source/core/rendering/shapes/Shape.cpp
diff --git a/Source/core/rendering/shapes/Shape.cpp b/Source/core/rendering/shapes/Shape.cpp
index 7fcb1d13f014b58af8e1f8fadd58ec5a8b1b1937..a6415e01846e8f18b3629168e2414b8b5e04fc61 100644
--- a/Source/core/rendering/shapes/Shape.cpp
+++ b/Source/core/rendering/shapes/Shape.cpp
@@ -37,6 +37,7 @@
 #include "core/rendering/shapes/RectangleShape.h"
 #include "platform/LengthFunctions.h"
 #include "platform/geometry/FloatSize.h"
+#include "platform/graphics/UnacceleratedImageBufferSurface.h"
 #include "platform/graphics/WindRule.h"
 #include "wtf/MathExtras.h"
 #include "wtf/OwnPtr.h"
@@ -210,15 +211,14 @@ PassOwnPtr<Shape> Shape::createShape(const StyleImage* styleImage, float thresho
 
     Image* image = styleImage->cachedImage()->image();
     const IntSize& imageSize = image->size();
-    OwnPtr<ImageBuffer> imageBuffer = ImageBuffer::create(imageSize);
-
     OwnPtr<RasterShapeIntervals> intervals = adoptPtr(new RasterShapeIntervals(imageSize.height()));
-
-    if (imageBuffer) {
-        GraphicsContext* graphicsContext = imageBuffer->context();
+    OwnPtr<ImageBufferSurface> surface = adoptPtr(new UnacceleratedImageBufferSurface(imageSize));
+    if (surface->isValid()) {
+        ImageBuffer imageBuffer(surface.release());
+        GraphicsContext* graphicsContext = imageBuffer.context();
         graphicsContext->drawImage(image, IntPoint());
 
-        RefPtr<Uint8ClampedArray> pixelArray = imageBuffer->getUnmultipliedImageData(IntRect(IntPoint(), imageSize));
+        RefPtr<Uint8ClampedArray> pixelArray = imageBuffer.getUnmultipliedImageData(IntRect(IntPoint(), imageSize));
         unsigned pixelArrayLength = pixelArray->length();
         unsigned pixelArrayOffset = 3; // Each pixel is four bytes: RGBA.
         uint8_t alphaPixelThreshold = threshold * 255;