[InputEvent] Add InputEvent with basic interface behind a flag

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 1071 matching lines @@
         SVGZoomEvent = 1232,
         V8Animation_Oncancel_AttributeGetter = 1233,
         V8Animation_Oncancel_AttributeSetter = 1234,
         V8HTMLCommentInExternalScript = 1235,
         V8HTMLComment = 1236,
         V8SloppyModeBlockScopedFunctionRedefinition = 1237,
         V8ForInInitializer = 1238,
         V8Animation_Id_AttributeGetter = 1239,
         V8Animation_Id_AttributeSetter = 1240,
         MediaStreamOnEnded = 1241,
+        DocumentCreateEventInputEvent = 1242,
 
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         // Also, run update_use_counter_feature_enum.py in chromium/src/tools/metrics/histograms/
         // to update the UMA mapping.
         NumberOfFeatures, // This enum value must be last.
     };
 
     // "count" sets the bit for this feature to 1. Repeated calls are ignored.
     static void count(const Frame*, Feature);
@@ skipping 70 matching lines @@
     friend class UseCounterTest;
     static int m_muteCount;
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h