Added available bit to m_selectorIndex.

third_party/WebKit/Source/core/css/RuleSet.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
  *
@@ skipping 93 matching lines @@
   // and good filtering performance.
   static const unsigned maximumIdentifierCount = 4;
   const unsigned* descendantSelectorIdentifierHashes() const {
     return m_descendantSelectorIdentifierHashes;
   }
 
   DECLARE_TRACE();
 
  private:
   Member<StyleRule> m_rule;
-  unsigned m_selectorIndex : 13;
-  // We store an array of RuleData objects in a primitive array.
-  unsigned m_isLastInArray : 1;
+  // This number is picked fairly arbitrary. If lowered, be aware that there
+  // might be sites and extensions using style rules with selector lists
+  // exceeding the number of simple selectors to fit in this bitfield.
+  // See https://crbug.com/312913 and https://crbug.com/704562
+  unsigned m_selectorIndex : 14;
   // This number was picked fairly arbitrarily. We can probably lower it if we
   // need to. Some simple testing showed <100,000 RuleData's on large sites.
   unsigned m_position : 18;
+  // 32 bits above
   unsigned m_specificity : 24;
   unsigned m_containsUncommonAttributeSelector : 1;
   unsigned m_linkMatchType : 2;  //  CSSSelector::LinkMatchMask
   unsigned m_hasDocumentSecurityOrigin : 1;
   unsigned m_propertyWhitelist : 2;
+  // We store an array of RuleData objects in a primitive array.
+  unsigned m_isLastInArray : 1;
+  // 31 bits above
   // Use plain array instead of a Vector to minimize memory overhead.
   unsigned m_descendantSelectorIdentifierHashes[maximumIdentifierCount];
 };
 
 }  // namespace blink
 
 WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::RuleData);
 
 namespace blink {
 
@@ skipping 177 matching lines @@
   Member<PendingRuleMaps> m_pendingRules;
 
 #ifndef NDEBUG
   HeapVector<RuleData> m_allRules;
 #endif
 };
 
 }  // namespace blink
 
 #endif  // RuleSet_h