Stop explicit inheritance if LayoutStyle doesn't change.

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 1354 matching lines @@
 
     unsigned cacheHash = matchResult.isCacheable ? computeMatchedPropertiesHash(matchResult.matchedProperties.data(), matchResult.matchedProperties.size()) : 0;
     bool applyInheritedOnly = false;
     const CachedMatchedProperties* cachedMatchedProperties = cacheHash ? m_matchedPropertiesCache.find(cacheHash, state, matchResult) : 0;
 
     if (cachedMatchedProperties && MatchedPropertiesCache::isCacheable(element, *state.style(), *state.parentStyle())) {
         INCREMENT_STYLE_STATS_COUNTER(*this, matchedPropertyCacheHit);
         // We can build up the style by copying non-inherited properties from an earlier style object built using the same exact
         // style declarations. We then only need to apply the inherited properties, if any, as their values can depend on the
         // element context. This is fast and saves memory by reusing the style data structures.
-        state.style()->copyNonInheritedFrom(*cachedMatchedProperties->layoutStyle);
+        state.style()->copyNonInheritedFromCached(*cachedMatchedProperties->layoutStyle);
         if (state.parentStyle()->inheritedDataShared(*cachedMatchedProperties->parentLayoutStyle) && !isAtShadowBoundary(element)
             && (!state.distributedToInsertionPoint() || state.style()->userModify() == READ_ONLY)) {
             INCREMENT_STYLE_STATS_COUNTER(*this, matchedPropertyCacheInheritedHit);
 
             EInsideLink linkStatus = state.style()->insideLink();
             // If the cache item parent style has identical inherited properties to the current parent style then the
             // resulting style will be identical too. We copy the inherited properties over from the cache and are done.
             state.style()->inheritFrom(*cachedMatchedProperties->layoutStyle);
 
             // Unfortunately the link status is treated like an inherited property. We need to explicitly restore it.
@@ skipping 161 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingRules);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink