Stop firing orientationchange events at pages that are not visible

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 148 matching lines @@
         else
             m_view->setVisibleContentScaleFactor(page()->pageScaleFactor());
     }
 }
 
 void LocalFrame::sendOrientationChangeEvent()
 {
     if (!RuntimeEnabledFeatures::orientationEventEnabled() && !RuntimeEnabledFeatures::screenOrientationEnabled())
         return;
 
+    if (page()->visibilityState() != PageVisibilityStateVisible)
+        return;
+
     DOMWindow* window = domWindow();
     if (!window)
         return;
     window->dispatchEvent(Event::create(EventTypeNames::orientationchange));
 
     // Notify subframes.
     Vector<RefPtr<LocalFrame> > childFrames;
     for (LocalFrame* child = tree().firstChild(); child; child = child->tree().nextSibling())
         childFrames.append(child);
 
@@ skipping 471 matching lines @@
 LocalFrame* LocalFrame::localFrameRoot()
 {
     LocalFrame* curFrame = this;
     while (curFrame && curFrame->tree().parent() && curFrame->tree().parent()->isLocalFrame())
         curFrame = curFrame->tree().parent();
 
     return curFrame;
 }
 
 } // namespace WebCore