Remove webkitdropzone.

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 335 matching lines @@
 
     UseAsm = 473,
     DOMWindowOpen = 475,
     DOMWindowOpenFeatures = 476,
     AspectRatioFlexItem = 479,
     DetailsElement = 480,
     DialogElement = 481,
     MapElement = 482,
     MeterElement = 483,
     ProgressElement = 484,
-    PrefixedHTMLElementDropzone = 490,
     WheelEventWheelDeltaX = 491,
     WheelEventWheelDeltaY = 492,
     WheelEventWheelDelta = 493,
     SendBeacon = 494,
     SendBeaconQuotaExceeded = 495,
     SVGSMILElementInDocument = 501,
     MouseEventOffsetX = 502,
     MouseEventOffsetY = 503,
     MouseEventX = 504,
     MouseEventY = 505,
@@ skipping 1206 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