cc: Partial tile update for one-copy raster.

cc/resources/tile_task_worker_pool.h

 // Copyright 2013 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_TILE_TASK_WORKER_POOL_H_
 #define CC_RESOURCES_TILE_TASK_WORKER_POOL_H_
 
 #include "cc/resources/tile_task_runner.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
@@ skipping 36 matching lines @@
 
   // Utility function that can be used to build a task graph. Inserts nodes that
   // represent |task| and all its image decode dependencies in |graph|.
   static void InsertNodesForRasterTask(
       TaskGraph* graph,
       RasterTask* task,
       const ImageDecodeTask::Vector& decode_tasks,
       unsigned priority);
 
   // Utility function that will create a temporary bitmap and copy pixels to
-  // |memory| when necessary.
+  // |memory| when necessary. The |canvas_bitmap_rect| is the rect of the bitmap
+  // being played back in the pixel space of the source, ie a rect in the source
+  // that will cover the resulting |memory|. The |canvas_playback_rect| can be a
+  // smaller contained rect inside the |canvas_bitmap_rect| if the |memory| is
+  // already partially complete, and only the subrect needs to be played back.
   static void PlaybackToMemory(void* memory,
                                ResourceFormat format,
                                const gfx::Size& size,
                                int stride,
                                const RasterSource* raster_source,
-                               const gfx::Rect& rect,
+                               const gfx::Rect& canvas_bitmap_rect,
+                               const gfx::Rect& canvas_playback_rect,
                                float scale);
 
   // Type-checking downcast routine.
   virtual TileTaskRunner* AsTileTaskRunner() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TILE_TASK_WORKER_POOL_H_