Conditionally update FontSelector on invalidation.

Source/platform/fonts/FontFallbackList.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 40 matching lines @@
 
 void FontFallbackList::invalidate(PassRefPtrWillBeRawPtr<FontSelector> fontSelector)
 {
     releaseFontData();
     m_fontList.clear();
     m_pageZero = 0;
     m_pages.clear();
     m_cachedPrimarySimpleFontData = 0;
     m_familyIndex = 0;
     m_hasLoadingFallback = false;
-    m_fontSelector = fontSelector;
+    if (m_fontSelector != fontSelector)
+        m_fontSelector = fontSelector;
     m_fontSelectorVersion = m_fontSelector ? m_fontSelector->version() : 0;
     m_generation = FontCache::fontCache()->generation();
     m_cachingWordShaper.clear();
 }
 
 void FontFallbackList::releaseFontData()
 {
     unsigned numFonts = m_fontList.size();
     for (unsigned i = 0; i < numFonts; ++i) {
         if (!m_fontList[i]->isCustomFont()) {
@@ skipping 144 matching lines @@
 
 bool FontFallbackList::isValid() const
 {
     if (!m_fontSelector)
         return m_fontSelectorVersion == 0;
 
     return m_fontSelector->version() == m_fontSelectorVersion;
 }
 
 } // namespace blink