The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec

commit 5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec
Author: tkent <tkent@chromium.org>
Date: Mon May 16 02:27:09 2016

Add UseCounters for Event.cancelBubble behavior.

https://github.com/whatwg/dom/issues/211#issuecomment-209395525
> 1. How often cancelBubble is changed from false to true (likely common) and
>   from true to false (hopefully rare).
> 2. How often the cancelBubble flag actually changes which callbacks are
>   invoked (hopefully rare).

BUG= 603377 
TBR=isherman@chromium.org

Review-Url: https://codereview.chromium.org/1972053002
Cr-Commit-Position: refs/heads/master@{#393784}

[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/core/events/Event.cpp
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/core/events/Event.h
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/core/events/Event.idl
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/core/events/EventDispatcher.cpp
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/third_party/WebKit/Source/modules/indexeddb/IDBEventDispatcher.cpp
[modify] https://crrev.com/5cc4cd4c058dbcb324ccf18d6e3b7ce1cea532ec/tools/metrics/histograms/histograms.xml