cc: Regenerate image decode requests tasks when cache switches.

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 68 matching lines @@
     scoped_refptr<TileTask> task;
     bool need_unref;
   };
 
   void StopWorkerTasks();
 
   // Called from the worker thread.
   void ProcessNextImageDecodeOnWorkerThread();
 
   void ImageDecodeCompleted(ImageDecodeRequestId id);
+  void GenerateTasksForOrphanedRequests();
 
   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;
 
   // 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;
+  // Orphaned requests are requests that were either in queue or needed a
+  // completion callback when we set the decode cache to be nullptr. When a new
+  // decode cache is set, these requests are re-enqueued again with tasks
+  // generated by the new cache. Note that when the cache is set, then aside
+  // from generating new tasks, this vector should be empty.
+  std::vector<ImageDecodeRequest> orphaned_decode_requests_;
 
   base::WeakPtrFactory<ImageController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageController);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_CONTROLLER_H_