Code: bool isUserInteractionEventForSlider(Event* event, LayoutObject* layoutObject) {
  if (isUserInteractionEvent(event))
    return true;

  LayoutSliderItem slider = LayoutSliderItem(toLayoutSlider(layoutObject));
  if (!slider.isNull() && !slider.inDragMode())
    return false;
 
   const AtomicString& type = event->type();
   return type == EventTypeNames::mouseover ||
         type == EventTypeNames::mouseout || type == EventTypeNames::mousemove;
 }

Vulnerability Type: DoS Overflow 
CWE ID: CWE-119
Summary: PDFium, as used in Google Chrome before 44.0.2403.89, does not properly handle certain out-of-memory conditions, which allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted PDF document that triggers a large memory allocation.
Commit Message: Fixed volume slider element event handling

MediaControlVolumeSliderElement::defaultEventHandler has making
redundant calls to setVolume() & setMuted() on mouse activity. E.g. if
a mouse click changed the slider position, the above calls were made 4
times, once for each of these events: mousedown, input, mouseup,
DOMActive, click. This crack got exposed when PointerEvents are enabled
by default on M55, adding pointermove, pointerdown & pointerup to the
list.

This CL fixes the code to trigger the calls to setVolume() & setMuted()
only when the slider position is changed. Also added pointer events to
certain lists of mouse events in the code.

BUG=677900

Review-Url: https://codereview.chromium.org/2622273003
Cr-Commit-Position: refs/heads/master@{#446032}