Don't update global ruleset when active style is dirty.

third_party/WebKit/Source/core/dom/StyleEngine.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 297 matching lines @@
       UnorderedTreeScopeSet& treeScopesRemoved);
 
   bool shouldSkipInvalidationFor(const Element&) const;
   void scheduleRuleSetInvalidationsForElement(
       Element&,
       const HeapHashSet<Member<RuleSet>>&);
   void invalidateSlottedElements(HTMLSlotElement&);
 
   void updateViewport();
   void updateActiveStyleSheets();
+  void updateGlobalRuleSet() {
+    DCHECK(!needsActiveStyleSheetUpdate());
+    m_globalRuleSet.update(document());
+  }
   const MediaQueryEvaluator& ensureMediaQueryEvaluator();
 
   Member<Document> m_document;
   bool m_isMaster;
 
   // Track the number of currently loading top-level stylesheets needed for
   // layout.  Sheets loaded using the @import directive are not included in this
   // count.  We use this count of pending sheets to detect when we can begin
   // attaching elements and when it is safe to execute scripts.
   int m_pendingScriptBlockingStylesheets = 0;
@@ skipping 38 matching lines @@
 
   std::unique_ptr<StyleResolverStats> m_styleResolverStats;
   unsigned m_styleForElementCount = 0;
 
   friend class StyleEngineTest;
 };
 
 }  // namespace blink
 
 #endif