Don't trigger full active style update on styleSheets access.

third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.h

 /*
  * 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, 2010, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 36 matching lines @@
     style_sheet_candidate_nodes_.Remove(&node);
   }
   bool HasStyleSheetCandidateNodes() const {
     return !style_sheet_candidate_nodes_.IsEmpty();
   }
   bool HasStyleSheets() const;
 
   bool MediaQueryAffectingValueChanged();
 
   virtual bool IsShadowTreeStyleSheetCollection() const { return false; }
-  void CollectStyleSheetsForList();
+  void UpdateStyleSheetList();
 
   DECLARE_VIRTUAL_TRACE();
 
  protected:
   explicit TreeScopeStyleSheetCollection(TreeScope&);
 
   Document& GetDocument() const { return GetTreeScope().GetDocument(); }
   TreeScope& GetTreeScope() const { return *tree_scope_; }
 
   void ApplyActiveStyleSheetChanges(StyleSheetCollection&);
 
   Member<TreeScope> tree_scope_;
   DocumentOrderedList style_sheet_candidate_nodes_;
 
  private:
   friend class TreeScopeStyleSheetCollectionTest;
 };
 
 }  // namespace blink
 
 #endif