cc: Reorder TileManager shutdown and add debugging information.

This patch changes the order of shutdown from clearing orphans then
completing tasks to first complete the tasks then clean orphans, since
task completion causes more orphans to be generated.

Also, this adds debugging information to ImageManager to narrow down
the time when crash in the referenced bug happens.

R=ericrk@chromium.org
BUG=650234
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel

Review-Url: https://codereview.chromium.org/2365303003
Cr-Commit-Position: refs/heads/master@{#421261}

cc/tiles/image_manager.cc

@@ -11,14 +11,17 @@ ImageManager::~ImageManager() = default;
 
 void ImageManager::SetImageDecodeController(ImageDecodeController* controller) {
   // We can only switch from null to non-null and back.
-  DCHECK(controller || controller_);
-  DCHECK(!controller || !controller_);
+  // CHECK to debug crbug.com/650234.
+  CHECK(controller || controller_);
+  CHECK(!controller || !controller_);
 
   if (!controller) {
     SetPredecodeImages(std::vector<DrawImage>(),
                        ImageDecodeController::TracingInfo());
   }
   controller_ = controller;
+  // Debugging information for crbug.com/650234.
+  ++num_times_controller_was_set_;
 }
 
 void ImageManager::GetTasksForImagesAndRef(
@@ -41,7 +44,8 @@ void ImageManager::GetTasksForImagesAndRef(
 }
 
 void ImageManager::UnrefImages(const std::vector<DrawImage>& images) {
-  DCHECK(controller_);
+  // Debugging information for crbug.com/650234.
+  CHECK(controller_) << num_times_controller_was_set_;
   for (auto image : images)
     controller_->UnrefImage(image);
 }

cc/tiles/image_manager.h

@@ -36,6 +36,9 @@ class CC_EXPORT ImageManager {
   ImageDecodeController* controller_ = nullptr;
   std::vector<DrawImage> predecode_locked_images_;
 
+  // Debugging information for crbug.com/650234.
+  size_t num_times_controller_was_set_ = 0;
+
   DISALLOW_COPY_AND_ASSIGN(ImageManager);
 };
 

cc/tiles/tile_manager.cc

@@ -346,11 +346,11 @@ void TileManager::FinishTasksAndCleanUp() {
 
   raster_buffer_provider_->Shutdown();
 
+  tile_task_manager_->CheckForCompletedTasks();
+
   // Now that all tasks have been finished, we can clear any |orphan_tasks_|.
   orphan_tasks_.clear();
 
-  tile_task_manager_->CheckForCompletedTasks();
-
   FreeResourcesForReleasedTiles();
   CleanUpReleasedTiles();