cc: Add checker-imaging support to TileManager.

cc/tiles/image_controller.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_CONTROLLER_H_
 #define CC_TILES_IMAGE_CONTROLLER_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 34 matching lines @@
 
   // This function requests that the given image be decoded and locked. Once the
   // callback has been issued, it is passed an ID, which should be used to
   // unlock this image. It is up to the caller to ensure that the image is later
   // unlocked using UnlockImageDecode.
   // Virtual for testing.
   virtual ImageDecodeRequestId QueueImageDecode(
       sk_sp<const SkImage> image,
       const ImageDecodedCallback& callback);
 
+ protected:
+  scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
+
  private:
   struct ImageDecodeRequest {
     ImageDecodeRequest();
     ImageDecodeRequest(ImageDecodeRequestId id,
                        const DrawImage& draw_image,
                        const ImageDecodedCallback& callback,
                        scoped_refptr<TileTask> task,
                        bool need_unref);
     ImageDecodeRequest(ImageDecodeRequest&& other);
     ImageDecodeRequest(const ImageDecodeRequest& other);
@@ skipping 16 matching lines @@
 
   void ImageDecodeCompleted(ImageDecodeRequestId id);
 
   ImageDecodeCache* cache_ = nullptr;
   std::vector<DrawImage> predecode_locked_images_;
 
   static ImageDecodeRequestId s_next_image_decode_queue_id_;
   std::unordered_map<ImageDecodeRequestId, DrawImage> requested_locked_images_;
 
   base::SequencedTaskRunner* origin_task_runner_ = nullptr;
-  scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
 
   // The variables defined below this lock (aside from weak_ptr_factory_) can
   // only be accessed when the lock is acquired.
   base::Lock lock_;
   std::map<ImageDecodeRequestId, ImageDecodeRequest> image_decode_queue_;
   std::map<ImageDecodeRequestId, ImageDecodeRequest>
       requests_needing_completion_;
   bool abort_tasks_ = false;
 
   base::WeakPtrFactory<ImageController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageController);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_CONTROLLER_H_