cc: Simplify task and its derived classes.

cc/raster/raster_buffer.h

Index: cc/raster/raster_buffer.h
diff --git a/cc/raster/raster_buffer.h b/cc/raster/raster_buffer.h
index 04972f9d73e11117f81753977b4289ef260c3997..2f132f09af6ad0ff3306e151cf066f88d1155c7e 100644
--- a/cc/raster/raster_buffer.h
+++ b/cc/raster/raster_buffer.h
@@ -7,11 +7,26 @@
 
 #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: