Added available bit to m_selectorIndex.

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

Index: third_party/WebKit/Source/core/css/RuleSet.h
diff --git a/third_party/WebKit/Source/core/css/RuleSet.h b/third_party/WebKit/Source/core/css/RuleSet.h
index d8ad82f5ffeee46b824cabbe4bc426fdbc347b18..d6530ff771d2831e3fcdde1a5f064d171da59ed6 100644
--- a/third_party/WebKit/Source/core/css/RuleSet.h
+++ b/third_party/WebKit/Source/core/css/RuleSet.h
@@ -111,17 +111,23 @@ class CORE_EXPORT RuleData {
 
  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];
 };