cc: Fix cleanup path for image decode requests in ImageController.

cc/tiles/image_controller.cc

 // 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.
 
 #include "cc/tiles/image_controller.h"
 
 #include "base/bind.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 59 matching lines @@
     cache_->UnrefImage(image_pair.second);
   requested_locked_images_.clear();
 
   // Now, complete the tasks that already ran but haven't completed. These would
   // be posted in the run loop, but since we invalidated the weak ptrs, we need
   // to run everything manually.
   for (auto& request_to_complete : requests_needing_completion_) {
     ImageDecodeRequestId id = request_to_complete.first;
     ImageDecodeRequest& request = request_to_complete.second;
 
-    // The task (if one exists) would have run already, so we just need to
-    // complete it.
-    if (request.task)
+    // The task (if one exists) would have run already, we just need to make
+    // sure it was completed. Multiple requests for the same image use the same
+    // task so it could have already been completed.
+    if (request.task && !request.task->HasCompleted())
       request.task->DidComplete();
 
     // Issue the callback, and unref the image immediately. This is so that any
     // code waiting on the callback can proceed, although we're breaking the
     // promise of having this image decoded. This is unfortunate, but it seems
     // like the least complexity to process an image decode controller becoming
     // nullptr.
     request.callback.Run(id);
     if (request.need_unref)
       cache_->UnrefImage(request.draw_image);
   }
   requests_needing_completion_.clear();
 
   // Finally, complete all of the tasks that never started running. This is
   // similar to the |requests_needing_completion_|, but happens at a different
   // stage in the pipeline.
   for (auto& request_pair : image_decode_queue_) {
     ImageDecodeRequestId id = request_pair.first;
     ImageDecodeRequest& request = request_pair.second;
 
     if (request.task) {
       // This task may have run via a different request, so only cancel it if
       // it's "new". That is, the same task could have been referenced by
       // several different image deque requests for the same image.
       if (request.task->state().IsNew())
         request.task->state().DidCancel();
-      request.task->DidComplete();
+
+      if (!request.task->HasCompleted())
+        request.task->DidComplete();
     }
     // Run the callback and unref the image.
     request.callback.Run(id);
     cache_->UnrefImage(request.draw_image);
   }
   image_decode_queue_.clear();
 }
 
 void ImageController::SetImageDecodeCache(ImageDecodeCache* cache) {
+  DCHECK(!cache_ || !cache);
+
   if (!cache) {
     SetPredecodeImages(std::vector<DrawImage>(),
                        ImageDecodeCache::TracingInfo());
     StopWorkerTasks();
   }
+
   cache_ = cache;
 }
 
 void ImageController::GetTasksForImagesAndRef(
     std::vector<DrawImage>* images,
     std::vector<scoped_refptr<TileTask>>* tasks,
     const ImageDecodeCache::TracingInfo& tracing_info) {
   DCHECK(cache_);
   for (auto it = images->begin(); it != images->end();) {
     scoped_refptr<TileTask> task;
@@ skipping 174 matching lines @@
 ImageController::ImageDecodeRequest::ImageDecodeRequest(
     const ImageDecodeRequest& other) = default;
 ImageController::ImageDecodeRequest::~ImageDecodeRequest() = default;
 
 ImageController::ImageDecodeRequest& ImageController::ImageDecodeRequest::
 operator=(ImageDecodeRequest&& other) = default;
 ImageController::ImageDecodeRequest& ImageController::ImageDecodeRequest::
 operator=(const ImageDecodeRequest& other) = default;
 
 }  // namespace cc