[Media Controls] Add UMA for timeline scrubber

third_party/WebKit/Source/core/html/shadow/SliderThumbElement.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 323 matching lines @@
     return;
   }
 }
 
 void SliderContainerElement::handleTouchEvent(TouchEvent* event) {
   HTMLInputElement* input = hostInput();
   if (input->isDisabledFormControl())
     return;
 
   if (event->type() == EventTypeNames::touchend) {
+    // TODO: Also do this for touchcancel?
     input->dispatchFormControlChangeEvent();
     event->setDefaultHandled();
     m_slidingDirection = NoMove;
     m_touchStarted = false;
     return;
   }
 
   // The direction of this series of touch actions has been determined, which is
   // perpendicular to the slider, so no need to adjust the value.
   if (!canSlide()) {
@@ skipping 101 matching lines @@
   updateTouchEventHandlerRegistry();
   HTMLElement::didMoveToNewDocument(oldDocument);
 }
 
 void SliderContainerElement::removeAllEventListeners() {
   Node::removeAllEventListeners();
   m_hasTouchEventHandler = false;
 }
 
 }  // namespace blink