Refactor the PlatformContext layer to have only one class.

skia/ext/vector_canvas.h

Index: skia/ext/vector_canvas.h
diff --git a/skia/ext/vector_canvas.h b/skia/ext/vector_canvas.h
index 897ffd46b7c61a60e0ceae8c364feb0968374c76..510e8f30fa7e9bc77cd893552aae0f26fe26c2b8 100644
--- a/skia/ext/vector_canvas.h
+++ b/skia/ext/vector_canvas.h
@@ -5,8 +5,8 @@
 #ifndef SKIA_EXT_VECTOR_CANVAS_H_
 #define SKIA_EXT_VECTOR_CANVAS_H_
 
-#include "skia/ext/platform_canvas_win.h"
-#include "skia/ext/vector_device.h"
+#include "skia/ext/platform_canvas.h"
+#include "skia/ext/vector_platform_device_win.h"
 
 namespace skia {
 
@@ -14,7 +14,7 @@ namespace skia {
 // to work with a VectorDevice to manage platform-specific drawing. It allows
 // using both Skia operations and platform-specific operations. It *doesn't*
 // support reading back from the bitmap backstore since it is not used.
-class VectorCanvas : public PlatformCanvasWin {
+class VectorCanvas : public PlatformCanvas {
  public:
   VectorCanvas();
   VectorCanvas(HDC dc, int width, int height);