cc: Move (partially) the predecode image tracking to ImageManager.

cc/tiles/image_manager.h

 // Copyright 2016 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_MANAGER_H_
 #define CC_TILES_IMAGE_MANAGER_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
   ImageManager();
   ~ImageManager();
 
   void SetImageDecodeController(ImageDecodeController* controller);
   void GetTasksForImagesAndRef(
       std::vector<DrawImage>* images,
       std::vector<scoped_refptr<TileTask>>* tasks,
       const ImageDecodeController::TracingInfo& tracing_info);
   void UnrefImages(const std::vector<DrawImage>& images);
   void ReduceMemoryUsage();
+  std::vector<scoped_refptr<TileTask>> SetPredecodeImages(
+      std::vector<DrawImage> predecode_images,
+      const ImageDecodeController::TracingInfo& tracing_info);
 
  private:
-  ImageDecodeController* controller_;
+  ImageDecodeController* controller_ = nullptr;
+  std::vector<DrawImage> predecode_locked_images_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_MANAGER_H_