Add page visibility observer for Geolocation

Source/modules/geolocation/GeolocationController.h

 /*
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 #ifndef GeolocationController_h
 #define GeolocationController_h
 
 #include "core/page/Page.h"
+#include "core/page/PageLifecycleObserver.h"
 #include "modules/geolocation/Geolocation.h"
 #include "wtf/HashSet.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 class GeolocationClient;
 class GeolocationError;
 class GeolocationPosition;
 class Page;
 
-class GeolocationController : public Supplement<Page> {
+class GeolocationController : public Supplement<Page>, public PageLifecycleObserver {
     WTF_MAKE_NONCOPYABLE(GeolocationController);
 public:
     ~GeolocationController();
 
     static PassOwnPtr<GeolocationController> create(Page*, GeolocationClient*);
 
     void addObserver(Geolocation*, bool enableHighAccuracy);
     void removeObserver(Geolocation*);
 
     void requestPermission(Geolocation*);
     void cancelPermissionRequest(Geolocation*);
 
     void positionChanged(GeolocationPosition*);
     void errorOccurred(GeolocationError*);
 
     GeolocationPosition* lastPosition();
 
     GeolocationClient* client() { return m_client; }
 
+    // Inherited from PageLifecycleObserver.
+    virtual void pageVisibilityChanged() OVERRIDE;
+
     static const char* supplementName();
     static GeolocationController* from(Page* page) { return static_cast<GeolocationController*>(Supplement<Page>::from(page, supplementName())); }
 
 private:
     GeolocationController(Page*, GeolocationClient*);
 
     GeolocationClient* m_client;
-    Page* m_page;
 
     RefPtr<GeolocationPosition> m_lastPosition;
     typedef HashSet<RefPtr<Geolocation> > ObserversSet;
     // All observers; both those requesting high accuracy and those not.
     ObserversSet m_observers;
     ObserversSet m_highAccuracyObservers;
 };
 
 } // namespace WebCore
 
 #endif // GeolocationController_h