Refactoring ImageBuffer to decouple it from Canvas2DLayerBridge

Source/core/platform/graphics/win/TransparencyWin.cpp

Index: Source/core/platform/graphics/win/TransparencyWin.cpp
diff --git a/Source/core/platform/graphics/win/TransparencyWin.cpp b/Source/core/platform/graphics/win/TransparencyWin.cpp
index 0b79aa3bc6ff2e82f4f06963d0f1cbb41c9fff9c..77a60d62a36222aa8b376fb46cdd26e092373b42 100644
--- a/Source/core/platform/graphics/win/TransparencyWin.cpp
+++ b/Source/core/platform/graphics/win/TransparencyWin.cpp
@@ -34,6 +34,7 @@
 #include "core/platform/graphics/SimpleFontData.h"
 #include "core/platform/graphics/skia/SkiaUtils.h"
 #include "core/platform/graphics/win/TransparencyWin.h"
+#include "platform/graphics/UnacceleratedImageBufferSurface.h"
 
 #include "SkColorPriv.h"
 #include "skia/ext/platform_canvas.h"
@@ -101,7 +102,9 @@ class TransparencyWin::OwnedBuffers {
 public:
     OwnedBuffers(const IntSize& size, bool needReferenceBuffer)
     {
-        m_destBitmap = ImageBuffer::create(size, 1);
+        OwnPtr<ImageBufferSurface> surface = adoptPtr(new UnacceleratedImageBufferSurface(size));
+        if (surface->isValid())
+            m_destBitmap = adoptPtr(new ImageBuffer(surface.release()));
 
         if (needReferenceBuffer) {
             m_referenceBitmap.setConfig(SkBitmap::kARGB_8888_Config, size.width(), size.height());