Add UMA metric for tracking root level listeners for blocking touch.

third_party/WebKit/Source/core/input/EventHandler.h

 /*
  * Copyright (C) 2006, 2007, 2009, 2010, 2011 Apple 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 470 matching lines @@
     Member<Element> m_lastDeferredTapElement;
 
     // Only used with the ScrollCustomization runtime enabled feature.
     std::deque<int> m_currentScrollChain;
     // True iff some of the delta has been consumed for the current
     // scroll sequence in this frame, or any child frames. Only used
     // with ScrollCustomization. If some delta has been consumed, a
     // scroll which shouldn't propagate can't cause any element to
     // scroll other than the |m_previousGestureScrolledNode|.
     bool m_deltaConsumedForScrollSequence;
+
+    // True if waiting on first touch move after a touch start.
+    bool m_waitingForFirstTouchMove;
 };
 
 } // namespace blink
 
 WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(blink::EventHandler::TouchInfo);
 
 #endif // EventHandler_h