Move PlatformEventDispatcher implementations to the Oilpan heap.

Source/core/frame/PlatformEventDispatcher.cpp

 // Copyright 2014 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 "config.h"
 #include "core/frame/PlatformEventDispatcher.h"
 
 #include "core/frame/PlatformEventController.h"
 #include "wtf/TemporaryChange.h"
 
 namespace blink {
 
 PlatformEventDispatcher::PlatformEventDispatcher()
     : m_needsPurge(false)
     , m_isDispatching(false)
 {
 }
 
-PlatformEventDispatcher::~PlatformEventDispatcher()
-{
-}
-
 void PlatformEventDispatcher::addController(PlatformEventController* controller)
 {
     bool wasEmpty = m_controllers.isEmpty();
     if (!m_controllers.contains(controller))
         m_controllers.append(controller);
     if (wasEmpty)
         startListening();
 }
 
 void PlatformEventDispatcher::removeController(PlatformEventController* controller)
@@ skipping 44 matching lines @@
         for (size_t i = 0; i < size; ++i) {
             if (m_controllers[i])
                 m_controllers[i]->didUpdateData();
         }
     }
 
     if (m_needsPurge)
         purgeControllers();
 }
 
+void PlatformEventDispatcher::trace(Visitor* visitor)
+{
+    visitor->trace(m_controllers);
+    visitor->registerWeakMembers<PlatformEventDispatcher, &PlatformEventDispatcher::clearWeakMembers>(this);
+}
+
+void PlatformEventDispatcher::clearWeakMembers(Visitor* visitor)
+{
+    for (size_t i = 0; i < m_controllers.size(); ++i) {
+        if (!visitor->isAlive(m_controllers[i])) {
+            m_controllers[i] = nullptr;
+            m_needsPurge = true;
+        }
+    }
+    // Next notification will purge the empty slots.
+}
+
 } // namespace blink