cc: Do bitmap conversion for RasterBuffer in the worker thread.

cc/resources/raster_buffer.h

+// Copyright 2014 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 CC_RESOURCES_RASTER_BUFFER_H_
+#define CC_RESOURCES_RASTER_BUFFER_H_
+
+#include "skia/ext/refptr.h"
+
+class SkCanvas;
+
+namespace cc {
+
+class RasterBuffer {
+ public:
+  virtual skia::RefPtr<SkCanvas> AcquireSkCanvas() = 0;
+  virtual void ReleaseSkCanvas(const skia::RefPtr<SkCanvas>& canvas) = 0;

[reveman, 2014/08/14 12:26:36]

const ref? That makes it seem like ReleaseSkCanvas is not going to modify it.
You're passing ownership so that's clearly not the case.

[auygun, 2014/08/15 09:20:40]

According to the documentation in skia/ext/refptr.h this is how to pass the
ownership.

// When passing around a ref-counted pointer to methods outside of Skia, always
// pass around the skia::RefPtr instead of the raw pointer. An example method
// that takes a SkShader* parameter and saves the SkShader* in the class.
//   void AMethodThatSavesAShader(const skia::RefPtr<SkShader>& shader) {
//     member_refptr_ = shader;
//   }
//   skia::RefPtr<SkShader> member_refptr_;

[reveman, 2014/08/15 11:54:31]

OK, we typically don't use const ref when passing ownership of a ref counted
type in chromium but if that's what skis does and as this is a skia type, we
should probably do that. Current patch looks good in this regard. Thanks for
pointing out that this is common practice in skia code.

[auygun, 2014/08/15 15:08:23]

Acknowledged.

+
+ protected:
+  virtual ~RasterBuffer() {}
+};
+
+}  // namespace cc
+
+#endif  // CC_RESOURCES_RASTER_BUFFER_H_