cc: Add image decode queue functionality to image manager.

cc/tiles/image_decode_cache.h

 // Copyright 2015 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_TILES_IMAGE_DECODE_CACHE_H_
 #define CC_TILES_IMAGE_DECODE_CACHE_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/playback/decoded_draw_image.h"
 #include "cc/playback/draw_image.h"
@@ skipping 43 matching lines @@
 
   // Fill in an TileTask which will decode the given image when run. In
   // case the image is already cached, fills in nullptr. Returns true if the
   // image needs to be unreffed when the caller is finished with it.
   //
   // This is called by the tile manager (on the compositor thread) when creating
   // a raster task.
   virtual bool GetTaskForImageAndRef(const DrawImage& image,
                                      const TracingInfo& tracing_info,
                                      scoped_refptr<TileTask>* task) = 0;
+  // Similar to GetTaskForImageAndRef, except that it returns tasks that are not
+  // meant to be run as part of raster. That is, this is part of a predecode
+  // API. Note that this should only return a task responsible for decoding (and
+  // not uploading), since it will be run on a worker thread which may not have
+  // the right GPU context for upload.
+  virtual bool GetOutOfRasterDecodeTaskForImageAndRef(
+      const DrawImage& image,
+      scoped_refptr<TileTask>* task) = 0;
+
   // Unrefs an image. When the tile is finished, this should be called for every
   // GetTaskForImageAndRef call that returned true.
   virtual void UnrefImage(const DrawImage& image) = 0;
 
   // Returns a decoded draw image. This may cause a decode if the image was not
   // predecoded.
   //
   // This is called by a raster task (on a worker thread) when an image is
   // required.
   virtual DecodedDrawImage GetDecodedImageForDraw(const DrawImage& image) = 0;
   // Unrefs an image. This should be called for every GetDecodedImageForDraw
   // when the draw with the image is finished.
   virtual void DrawWithImageFinished(const DrawImage& image,
                                      const DecodedDrawImage& decoded_image) = 0;
 
   // This function informs the cache that now is a good time to clean up
   // memory. This is called periodically from the compositor thread.
   virtual void ReduceCacheUsage() = 0;
 
   // This function informs the cache that we are hidden and should not be
   // retaining cached resources longer than needed.
   virtual void SetShouldAggressivelyFreeResources(
       bool aggressively_free_resources) = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_DECODE_CACHE_H_