Lose/restore WebGL contexts if multisampling blackist status changes at runtime.

Source/core/page/Page.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 241 matching lines @@
     AlternativeTextClient* alternativeTextClient() const { return m_alternativeTextClient; }
 
     PageConsole* console() { return m_console.get(); }
 
     void reportMemoryUsage(MemoryObjectInfo*) const;
 
     void captionPreferencesChanged();
 
     double timerAlignmentInterval() const;
 
+    class MultisamplingChangedObserver {
+    public:
+        MultisamplingChangedObserver(Page*);
+        virtual void multisamplingChanged(bool) = 0;
+        virtual ~MultisamplingChangedObserver();
+    private:
+        Page* m_page;
+    };
+
+    friend class MultisamplingChangedObserver;
+
+    void multisamplingChanged();
+
 private:
     void initGroup();
 
 #if ASSERT_DISABLED
     void checkSubframeCountConsistency() const { }
 #else
     void checkSubframeCountConsistency() const;
 #endif
 
     void setTimerAlignmentInterval(double);
@@ skipping 60 matching lines @@
     Region m_topRelevantPaintedRegion;
     Region m_bottomRelevantPaintedRegion;
     Region m_relevantUnpaintedRegion;
     bool m_isCountingRelevantRepaintedObjects;
 #ifndef NDEBUG
     bool m_isPainting;
 #endif
     AlternativeTextClient* m_alternativeTextClient;
 
     OwnPtr<PageConsole> m_console;
+
+    HashSet<MultisamplingChangedObserver*> m_multisamplingChangedObservers;
 };
 
 } // namespace WebCore
     
 #endif // Page_h