Cleanup: Add more conversion helpers for usage.

Source/modules/device_orientation/NewDeviceOrientationController.cpp

 /*
  * Copyright 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
@@ skipping 71 matching lines @@
     DeviceOrientationDispatcher::instance().addDeviceOrientationController(this);
 }
 
 void NewDeviceOrientationController::unregisterWithDispatcher()
 {
     DeviceOrientationDispatcher::instance().removeDeviceOrientationController(this);
 }
 
 bool NewDeviceOrientationController::isNullEvent(Event* event)
 {
-    ASSERT(event->type() == EventNames::deviceorientation);
-    DeviceOrientationEvent* orientationEvent = static_cast<DeviceOrientationEvent*>(event);
+    DeviceOrientationEvent* orientationEvent = toDeviceOrientationEvent(event);
     return !orientationEvent->orientation()->canProvideEventData();
 }
 
 void NewDeviceOrientationController::didAddEventListener(DOMWindow* window, const AtomicString& eventType)
 {
     if (eventType == EventNames::deviceorientation && RuntimeEnabledFeatures::deviceOrientationEnabled())
         startUpdating();
 }
 
 void NewDeviceOrientationController::didRemoveEventListener(DOMWindow* window, const AtomicString& eventType)
 {
     if (eventType == EventNames::deviceorientation)
         stopUpdating();
 }
 
 void NewDeviceOrientationController::didRemoveAllEventListeners(DOMWindow* window)
 {
     stopUpdating();
 }
 
 } // namespace WebCore