cc: Simplify task and its derived classes.

cc/raster/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_RASTER_RASTER_BUFFER_H_
 #define CC_RASTER_RASTER_BUFFER_H_
 
 #include <stdint.h>
 
+#include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/playback/raster_source.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace cc {
+class RasterBuffer;
+class Resource;
+
+class CC_EXPORT RasterBufferProvider {
+ public:
+  virtual scoped_ptr<RasterBuffer> AcquireBufferForRaster(
+      const Resource* resource,
+      uint64_t resource_content_id,
+      uint64_t previous_content_id) = 0;
+  virtual void ReleaseBufferForRaster(scoped_ptr<RasterBuffer> buffer) = 0;
+
+ protected:
+  virtual ~RasterBufferProvider() {}
+};
 
 class CC_EXPORT RasterBuffer {
  public:
   RasterBuffer();
   virtual ~RasterBuffer();
 
   virtual void Playback(
       const RasterSource* raster_source,
       const gfx::Rect& raster_full_rect,
       const gfx::Rect& raster_dirty_rect,
       uint64_t new_content_id,
       float scale,
       const RasterSource::PlaybackSettings& playback_settings) = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_RASTER_BUFFER_H_