Fire null Device Motion events only once.

Source/modules/device_orientation/DeviceSensorEventController.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 17 matching lines @@
 #include "modules/device_orientation/DeviceSensorEventController.h"
 
 #include "core/dom/Document.h"
 #include "core/page/DOMWindow.h"
 
 namespace WebCore {
 
 DeviceSensorEventController::DeviceSensorEventController(Document* document)
     : m_document(document)
     , m_isActive(false)
+    , m_needsCheckingNullEvents(true)
     , m_timer(this, &DeviceSensorEventController::fireDeviceEvent)
 {
 }
 
 DeviceSensorEventController::~DeviceSensorEventController()
 {
     stopUpdating();
 }
 
 void DeviceSensorEventController::fireDeviceEvent(Timer<DeviceSensorEventController>* timer)
 {
     ASSERT_UNUSED(timer, timer == &m_timer);
     ASSERT(hasLastData());
 
     m_timer.stop();
     dispatchDeviceEvent(getLastEvent());
 }
 
 void DeviceSensorEventController::dispatchDeviceEvent(PassRefPtr<Event> prpEvent)
 {
     RefPtr<Event> event = prpEvent;
     if (m_document && m_document->domWindow()
         && !m_document->activeDOMObjectsAreSuspended()
         && !m_document->activeDOMObjectsAreStopped())
         m_document->domWindow()->dispatchEvent(event);
+
+    if (m_needsCheckingNullEvents) {
+        if (isNullEvent(event.get()))
+            stopUpdating();
+        else
+            m_needsCheckingNullEvents = false;
+    }
 }
 
 void DeviceSensorEventController::startUpdating()
 {
     if (m_isActive)
         return;
 
-    registerWithDispatcher();
-    m_isActive = true;
-
     if (hasLastData() && !m_timer.isActive()) {
         // Make sure to fire the device motion data as soon as possible.
         m_timer.startOneShot(0);
     }
+
+    registerWithDispatcher();
+    m_isActive = true;
 }
 
 void DeviceSensorEventController::stopUpdating()
 {
     if (!m_isActive)
         return;
 
+    if (m_timer.isActive())
+        m_timer.stop();
+
     unregisterWithDispatcher();
     m_isActive = false;
 }
 
 } // namespace WebCore