cc: Regenerate image decode requests tasks when cache switches.

cc/tiles/image_controller.h

Index: cc/tiles/image_controller.h
diff --git a/cc/tiles/image_controller.h b/cc/tiles/image_controller.h
index 4e8a57242342c44b8b0110c79b3b23c7dbf79d24..f62638a1c078679aa09597ebc75ec3f40395c7b5 100644
--- a/cc/tiles/image_controller.h
+++ b/cc/tiles/image_controller.h
@@ -86,6 +86,7 @@ class CC_EXPORT ImageController {
   void ProcessNextImageDecodeOnWorkerThread();
 
   void ImageDecodeCompleted(ImageDecodeRequestId id);
+  void GenerateTasksForOrphanedRequests();
 
   ImageDecodeCache* cache_ = nullptr;
   std::vector<DrawImage> predecode_locked_images_;
@@ -102,6 +103,12 @@ class CC_EXPORT ImageController {
   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_;