Avoid always style recalc when removing stylesheets.

Source/core/css/CSSStyleSheet.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 131 matching lines @@
 
     // Any existing CSSOM wrappers need to be connected to the copied child rules.
     reattachChildRuleCSSOMWrappers();
 }
 
 void CSSStyleSheet::didMutateRules()
 {
     ASSERT(m_contents->isMutable());
     ASSERT(m_contents->hasOneClient());
 
-    didMutate();
+    didMutate(PartialRuleUpdate);
 }
 
-void CSSStyleSheet::didMutate()
+void CSSStyleSheet::didMutate(StyleSheetUpdateType updateType)
 {
     Document* owner = ownerDocument();
     if (!owner)
         return;
-    owner->modifiedStyleSheet(this);
+
+    // Need FullStyleUpdate when insertRule or deleteRule,
+    // because StyleSheetCollection::analyzeStyleSheetChange cannot detect partial rule update.
+    StyleResolverUpdateMode updateMode = updateType != PartialRuleUpdate ? AnalyzedStyleUpdate : FullStyleUpdate;
+    owner->modifiedStyleSheet(this, RecalcStyleDeferred, updateMode);
 }
 
 void CSSStyleSheet::reattachChildRuleCSSOMWrappers()
 {
     for (unsigned i = 0; i < m_childRuleCSSOMWrappers.size(); ++i) {
         if (!m_childRuleCSSOMWrappers[i])
             continue;
         m_childRuleCSSOMWrappers[i]->reattach(m_contents->ruleAt(i));
     }
 }
@@ skipping 188 matching lines @@
         root = root->parentStyleSheet();
     return root->ownerNode() ? &root->ownerNode()->document() : 0;
 }
 
 void CSSStyleSheet::clearChildRuleCSSOMWrappers()
 {
     m_childRuleCSSOMWrappers.clear();
 }
 
 }