cc: Reorder TileManager shutdown and add debugging information.

cc/tiles/image_manager.h

Index: cc/tiles/image_manager.h
diff --git a/cc/tiles/image_manager.h b/cc/tiles/image_manager.h
index 046e0948e8bda2775cace12819247934828f59db..13940a81d3fbe64b37909d834acc0de5feba3e93 100644
--- a/cc/tiles/image_manager.h
+++ b/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);
 };