Count usage of the obsolete 'isindex' element.

Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 247 matching lines @@
         PrefixedPageVisibility,
         HTMLFrameElementLocation,
         CSSStyleSheetInsertRuleOptionalArg, // Inconsistent with the specification and other browsers.
         CSSWebkitRegionAtRule, // @region rule changed to ::region()
         DocumentBeforeUnloadRegistered,
         DocumentBeforeUnloadFired,
         DocumentUnloadRegistered,
         DocumentUnloadFired,
         SVGLocatableNearestViewportElement,
         SVGLocatableFarthestViewportElement,
+        IsIndexElement,
         // Add new features immediately above this line. Don't change assigned
         // numbers of each items, and don't reuse unused slots.
         NumberOfFeatures, // This enum value must be last.
     };
 
     // "count" sets the bit for this feature to 1. Repeated calls are ignored.
     static void count(const Document&, Feature);
     static void count(const DOMWindow*, Feature);
     void count(CSSParserContext, CSSPropertyID);
     void count(Feature);
@@ skipping 35 matching lines @@
 
     void updateMeasurements();
 
     OwnPtr<BitVector> m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace WebCore
 
 #endif // UseCounter_h