Evaluate MediaQueryLists on actual media changes only.

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 662 matching lines @@
 
 MediaQueryMatcher& Document::mediaQueryMatcher()
 {
     if (!m_mediaQueryMatcher)
         m_mediaQueryMatcher = MediaQueryMatcher::create(this);
     return *m_mediaQueryMatcher;
 }
 
 void Document::mediaQueryAffectingValueChanged()
 {
+    m_evaluateMediaQueriesOnStyleRecalc = true;
     styleEngine()->clearMediaQueryRuleSetStyleSheets();
 }
 
 void Document::setCompatibilityMode(CompatibilityMode mode)
 {
     if (m_compatibilityModeLocked || mode == m_compatibilityMode)
         return;
     bool wasInQuirksMode = inQuirksMode();
     m_compatibilityMode = mode;
     selectorQueryCache().invalidate();
@@ skipping 2756 matching lines @@
         return;
 
     m_styleEngine->resolverChanged(updateMode);
 
     if (didLayoutWithPendingStylesheets() && !m_styleEngine->hasPendingSheets()) {
         // We need to manually repaint because we avoid doing all repaints in layout or style
         // recalc while sheets are still loading to avoid FOUC.
         m_pendingSheetLayout = IgnoreLayoutWithPendingSheets;
         renderView()->repaintViewAndCompositedLayers();
     }
-
-    m_evaluateMediaQueriesOnStyleRecalc = true;
 }
 
 void Document::styleResolverMayHaveChanged()
 {
     styleResolverChanged(hasNodesWithPlaceholderStyle() ? FullStyleUpdate : AnalyzedStyleUpdate);
 }
 
 void Document::setHoverNode(PassRefPtrWillBeRawPtr<Node> newHoverNode)
 {
     m_hoverNode = newHoverNode;
@@ skipping 2383 matching lines @@
     visitor->trace(m_compositorPendingAnimations);
     visitor->trace(m_contextDocument);
     visitor->registerWeakMembers<Document, &Document::clearWeakMembers>(this);
     DocumentSupplementable::trace(visitor);
     TreeScope::trace(visitor);
     ContainerNode::trace(visitor);
     ExecutionContext::trace(visitor);
 }
 
 } // namespace WebCore