Oilpan: reliably track listening PlatformEventControllers.

Source/modules/battery/BatteryManager.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 "modules/battery/BatteryManager.h"
 
 #include "core/dom/Document.h"
 #include "core/events/Event.h"
 #include "modules/battery/BatteryDispatcher.h"
@@ skipping 71 matching lines @@
     m_batteryStatus = BatteryDispatcher::instance().latestData();
 
     if (m_state == Pending) {
         ASSERT(m_resolver);
         m_state = Resolved;
         m_resolver->resolve(this);
         return;
     }
 
     Document* document = toDocument(executionContext());
-    if (document->activeDOMObjectsAreSuspended() || document->activeDOMObjectsAreStopped())
+    if (!document || document->activeDOMObjectsAreSuspended() || document->activeDOMObjectsAreStopped())

[mlamouri (slow - plz ping), 2014/09/30 17:08:49]

Is there any situation where we expect !document? Should we assert instead?

         return;
 
     ASSERT(oldStatus);
 
     if (m_batteryStatus->charging() != oldStatus->charging())
         dispatchEvent(Event::create(EventTypeNames::chargingchange));
     if (m_batteryStatus->chargingTime() != oldStatus->chargingTime())
         dispatchEvent(Event::create(EventTypeNames::chargingtimechange));
     if (m_batteryStatus->dischargingTime() != oldStatus->dischargingTime())
         dispatchEvent(Event::create(EventTypeNames::dischargingtimechange));
@@ skipping 38 matching lines @@
 bool BatteryManager::hasPendingActivity() const
 {
     // Prevent V8 from garbage collecting the wrapper object if there are
     // event listeners attached to it.
     return m_state == Resolved && hasEventListeners();
 }
 
 void BatteryManager::trace(Visitor* visitor)
 {
     visitor->trace(m_batteryStatus);
+    PlatformEventController::trace(visitor);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink