Stop firing orientationchange events at pages that are not visible

Source/modules/screen_orientation/ScreenOrientation.h

Index: Source/modules/screen_orientation/ScreenOrientation.h
diff --git a/Source/modules/screen_orientation/ScreenOrientation.h b/Source/modules/screen_orientation/ScreenOrientation.h
index aaae462c2dda426426eabab804ccfbe66cd6df44..5afa8f6788ef0f7984f192794ee4ef55ccccdb3d 100644
--- a/Source/modules/screen_orientation/ScreenOrientation.h
+++ b/Source/modules/screen_orientation/ScreenOrientation.h
@@ -5,6 +5,7 @@
 #ifndef ScreenOrientation_h
 #define ScreenOrientation_h
 
+#include "core/dom/FullscreenObserver.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "platform/Supplementable.h"
 #include "platform/Timer.h"
@@ -18,7 +19,7 @@ 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&);
@@ -32,10 +33,17 @@ public:
 
 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;