[Media, Controls] Cleanup resize observer before dereferencing.

third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp

Index: third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
diff --git a/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp b/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
index 4a56a9f928556ceca271144191ea5bbdda43b259..7bc6352bbc12a346c8795bbd5dd7cc055a514be4 100644
--- a/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
+++ b/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
@@ -508,7 +508,10 @@ void MediaControlsImpl::RemovedFrom(ContainerNode*) {
   if (rotate_to_fullscreen_delegate_)
     rotate_to_fullscreen_delegate_->Detach();
 
-  resize_observer_.Clear();
+  if (resize_observer_) {
+    resize_observer_->disconnect();
+    resize_observer_.Clear();
+  }
 
   if (element_mutation_callback_) {
     element_mutation_callback_->Disconnect();