Stop firing orientationchange events at pages that are not visible

Source/modules/screen_orientation/ScreenOrientation.h

 // 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.
 
 #ifndef ScreenOrientation_h
 #define ScreenOrientation_h
 
+#include "core/dom/FullscreenObserver.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "platform/Supplementable.h"
 #include "platform/Timer.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebScreenOrientationLockType.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 class Document;
 class Screen;
 
-class ScreenOrientation FINAL : public NoBaseWillBeGarbageCollectedFinalized<ScreenOrientation>, public WillBeHeapSupplement<Screen>, DOMWindowProperty {
+class ScreenOrientation FINAL : public NoBaseWillBeGarbageCollectedFinalized<ScreenOrientation>, public WillBeHeapSupplement<Screen>, public DOMWindowProperty, public FullscreenObserver {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ScreenOrientation);
 public:
     static ScreenOrientation& from(Screen&);
     virtual ~ScreenOrientation();
 
     static const AtomicString& orientation(Screen&);
     static bool lockOrientation(Screen&, const AtomicString& orientation);
     static void unlockOrientation(Screen&);
 
     virtual void trace(Visitor* visitor) OVERRIDE { WillBeHeapSupplement<Screen>::trace(visitor); }
 
 private:
     explicit ScreenOrientation(Screen&);
+    bool isOrientationLockingAllowed(Document&) const;
 
     void lockOrientationAsync(blink::WebScreenOrientationLockType);
     void orientationLockTimerFired(Timer<ScreenOrientation>*);
 
+    void startListeningForFullscreenExit();
+    void stopListeningForFullscreenExit();
+
+    // FullscreenObserver API.
+    virtual void didFullyExitFullscreen() OVERRIDE;
+
     static const char* supplementName();
     Document* document() const;
 
     Timer<ScreenOrientation> m_orientationLockTimer;
     blink::WebScreenOrientationLockType m_prospectiveLock;
 };
 
 } // namespace WebCore
 
 #endif // ScreenOrientation_h