Allow CanvasSkia to bind to an existing SkCanvas.

skia/ext/canvas_paint_common.h

Index: skia/ext/canvas_paint_common.h
diff --git a/skia/ext/canvas_paint_common.h b/skia/ext/canvas_paint_common.h
new file mode 100644
index 0000000000000000000000000000000000000000..6eed3f4a5899417261a6258df925eb53bf882b40
--- /dev/null
+++ b/skia/ext/canvas_paint_common.h
@@ -0,0 +1,18 @@
+// Copyright (c) 2011 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_EXT_CANVAS_PAINT_COMMON_H_
+#define SKIA_EXT_CANVAS_PAINT_COMMON_H_
+#pragma once
+
+namespace skia {
+class PlatformCanvas;
+
+template<class T> inline PlatformCanvas* GetPlatformCanvas(T* t) {
+  return t;
+}
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_CANVAS_PAINT_COMMON_H_