(Re-)introduce AncestorThrottle to handle 'X-Frame-Options'.

third_party/WebKit/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 95 matching lines @@
     MinAttribute = 43,
     PatternAttribute = 44,
     PlaceholderAttribute = 45,
     PrefixedDirectoryAttribute = 47,
     RequiredAttribute = 49,
     StepAttribute = 51,
     PageVisits = 52,
     HTMLMarqueeElement = 53,
     Reflection = 55,
     PrefixedStorageInfo = 57,
-    XFrameOptions = 58,
-    XFrameOptionsSameOrigin = 59,
-    XFrameOptionsSameOriginWithBadAncestorChain = 60,
     DeprecatedFlexboxWebContent = 61,
     DeprecatedFlexboxChrome = 62,
     DeprecatedFlexboxChromeExtension = 63,
     UnprefixedPerformanceTimeline = 65,
     UnprefixedUserTiming = 67,
     WindowEvent = 69,
     ContentSecurityPolicyWithBaseElement = 70,
     DocumentClear = 74,
     XMLDocument = 77,
     XSLProcessingInstruction = 78,
@@ skipping 1338 matching lines @@
     // Tracks what features/properties need to be reported to the legacy
     // histograms.
     BitVector m_featureBits;
     BitVector m_CSSBits;
   } m_legacyCounter;
 };
 
 }  // namespace blink
 
 #endif  // UseCounter_h