Gracefully support Navigator Gamepad methods in a detached state.

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 "RuntimeEnabledFeatures.h"
 #include "core/events/Event.h"
 #include "modules/battery/BatteryDispatcher.h"
 #include "modules/battery/BatteryStatus.h"
 #include <limits>
 
 namespace WebCore {
 
 PassRefPtrWillBeRawPtr<BatteryManager> BatteryManager::create(ExecutionContext* context)
 {
     RefPtrWillBeRawPtr<BatteryManager> batteryManager(adoptRefWillBeRefCountedGarbageCollected(new BatteryManager(context)));
     batteryManager->suspendIfNeeded();
     return batteryManager.release();
 }
 
 BatteryManager::~BatteryManager()
 {
 }
 
 BatteryManager::BatteryManager(ExecutionContext* context)
     : ActiveDOMObject(context)
-    , DeviceSensorEventController(*toDocument(context))
+    , DeviceSensorEventController(toDocument(context)->page())
 {
     m_hasEventListener = true;
     startUpdating();
 }
 
 bool BatteryManager::charging()
 {
     if (const BatteryStatus* lastData = BatteryDispatcher::instance().getLatestData())
         return lastData->charging();
 
@@ skipping 50 matching lines @@
 {
     // Events are dispached via BatteryManager::didChangeBatteryStatus()
     return nullptr;
 }
 
 bool BatteryManager::isNullEvent(Event*)
 {
     return false;
 }
 
+Document* BatteryManager::document()
+{
+    return toDocument(executionContext());
+}
+
 void BatteryManager::suspend()
 {
     m_hasEventListener = false;
     stopUpdating();
 }
 
 void BatteryManager::resume()
 {
     m_hasEventListener = true;
     startUpdating();
 }
 
 void BatteryManager::stop()
 {
     m_hasEventListener = false;
     stopUpdating();
 }
 
 } // namespace WebCore