Add use counter for Long Task Observer

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 1319 matching lines @@
     CreateObjectURLMediaSource = 1605,
     CreateObjectURLMediaStream = 1606,
     DocumentCreateTouchWindowNull = 1607,
     DocumentCreateTouchWindowWrongType = 1608,
     DocumentCreateTouchTargetNull = 1609,
     DocumentCreateTouchTargetWrongType = 1610,
     DocumentCreateTouchLessThanSevenArguments = 1611,
     DocumentCreateTouchMoreThanSevenArguments = 1612,
     EncryptedMediaCapabilityProvided = 1613,
     EncryptedMediaCapabilityNotProvided = 1614,
+    LongTaskObserver = 1615,
 
     // 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 65 matching lines @@
    private:
     // 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