Oilpan: reliably track listening PlatformEventControllers.

Source/modules/gamepad/NavigatorGamepad.cpp

 /*
  * Copyright (C) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 111 matching lines @@
     return m_gamepads.get();
 }
 
 void NavigatorGamepad::trace(Visitor* visitor)
 {
     visitor->trace(m_gamepads);
     visitor->trace(m_webkitGamepads);
     visitor->trace(m_pendingEvents);
     WillBeHeapSupplement<Navigator>::trace(visitor);
     DOMWindowProperty::trace(visitor);
+    PlatformEventController::trace(visitor);
 }
 
 void NavigatorGamepad::didUpdateData()
 {
     // We should stop listening once we detached.
     ASSERT(window());
 
     // We register to the dispatcher before sampling gamepads so we need to check if we actually have an event listener.
     if (!m_hasEventListener)
         return;
@@ skipping 146 matching lines @@
         if (connectedGamepadChanged || (!oldWasConnected && newIsConnected)) {
             m_pendingEvents.append(newGamepad);
         }
     }
 
     if (!m_pendingEvents.isEmpty())
         m_dispatchOneEventRunner.runAsync();
 }
 
 } // namespace blink