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

Source/core/page/Page.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 808 matching lines @@
     info.ignoreMember(m_plugInClient);
     info.ignoreMember(m_validationMessageClient);
 }
 
 void Page::captionPreferencesChanged()
 {
     for (Frame* frame = mainFrame(); frame; frame = frame->tree()->traverseNext())
         frame->document()->captionPreferencesChanged();
 }
 
+void Page::addSettingsChangedObserver(SettingsChangedObserver* observer)
+{
+    m_settingsChangedObservers.add(observer);
+}
+
+void Page::removeSettingsChangedObserver(SettingsChangedObserver* observer)
+{
+    m_settingsChangedObservers.remove(observer);
+}
+
+void Page::settingsChanged() const
+{
+    HashSet<SettingsChangedObserver*>::iterator stop = m_settingsChangedObservers.end();
+    for (HashSet<SettingsChangedObserver*>::iterator it = m_settingsChangedObservers.begin(); it != stop; ++it)
+        (*it)->settingsChanged(m_settings.get());

[abarth-chromium, 2013/05/06 21:58:30]

This is a weak iteration pattern.  What if calling settingsChanged mutates
m_settingsChangedObservers?

+}
+
 Page::PageClients::PageClients()
     : alternativeTextClient(0)
     , chromeClient(0)
     , contextMenuClient(0)
     , editorClient(0)
     , dragClient(0)
     , inspectorClient(0)
     , plugInClient(0)
 {
 }
 
 Page::PageClients::~PageClients()
 {
 }
 
 } // namespace WebCore