Keep the cairo clipping region in sync with the Skia one.

skia/ext/bitmap_platform_device_win.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKIA_BITMAP_PLATFORM_DEVICE_WIN_H_
 #define SKIA_BITMAP_PLATFORM_DEVICE_WIN_H_
 
 #include "skia/ext/platform_device_win.h"
 
 namespace skia {
@@ skipping 46 matching lines @@
   // around to another routine willing to deal with the bitmap data directly.
   BitmapPlatformDevice(const BitmapPlatformDevice& other);
   virtual ~BitmapPlatformDevice();
 
   // See warning for copy constructor above.
   BitmapPlatformDevice& operator=(const BitmapPlatformDevice& other);
 
   // Retrieves the bitmap DC, which is the memory DC for our bitmap data. The
   // bitmap DC is lazy created.
   virtual HDC getBitmapDC();
+
+  // Loads the given transform and clipping region into the HDC. This is
+  // overridden from SkDevice.
   virtual void setMatrixClip(const SkMatrix& transform, const SkRegion& region);
 
   virtual void drawToHDC(HDC dc, int x, int y, const RECT* src_rect);
   virtual void makeOpaque(int x, int y, int width, int height);
   virtual bool IsVectorial() { return false; }
 
   // Returns the color value at the specified location. This does not
   // consider any transforms that may be set on the device.
   SkColor getColorAt(int x, int y);
 
@@ skipping 15 matching lines @@
 
   // Data associated with this device, guaranteed non-null. We hold a reference
   // to this object.
   BitmapPlatformDeviceData* data_;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_BITMAP_PLATFORM_DEVICE_WIN_H_