The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad

commit da8cf24a69567fbc9d2a594489d0ec0566a3d3ad
Author: Hayato Ito <hayato@chromium.org>
Date: Tue Sep 18 04:50:48 2018

Call capture event listeners in capturing phase at shadow hosts

Chromestatus entry is here: https://www.chromestatus.com/feature/5636327009681408

Per the discussion of https://github.com/whatwg/dom/issues/685, Blink will try to align the event
dispatch behavior with other browsers; Call capture event listeners in capturing phase at shadow
hosts.

So far, Blink and WebKit call capture event listeners in *bubbling* phase, instead of
*capturing* phase, at shadow hosts.

Other browsers:
- Safari: Will try to change the behavior in the next Safari Technical Preview.
- Firefox: Already implemented the new behavior
- Edge: Strong public support for the new behavior.

This change is guard by CallCaptureListenersAtCapturePhaseAtShadowHosts flag, which is disabled
at this moment, to confirm that this CL doesn't cause any behavior change when the flag is disabled.

This CL adds a wpt for new behavior, which is now marked as [Failure] in Blink.

After this CL lands, I will flip the flag in a follow-up CL, with rebasing a very few existing
tests.

BUG= 883650 

Change-Id: I29938840aed4f3430d8b749cd4843176b8668b5d
Reviewed-on: https://chromium-review.googlesource.com/1212255
Commit-Queue: Hayato Ito <hayato@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591939}
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/WebKit/LayoutTests/TestExpectations
[add] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/WebKit/LayoutTests/external/wpt/shadow-dom/event-dispatch-order.tentative.html
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/WebKit/LayoutTests/external/wpt/shadow-dom/resources/shadow-dom.js
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/dom/events/event.cc
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/dom/events/event.h
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/dom/events/event_dispatcher.cc
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/dom/events/event_target.cc
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/events/registered_event_listener.cc
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/core/events/registered_event_listener.h
[modify] https://crrev.com/da8cf24a69567fbc9d2a594489d0ec0566a3d3ad/third_party/blink/renderer/platform/runtime_enabled_features.json5

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/47241df2c1d09e6f875fbd1f82feed1320181cd6

commit 47241df2c1d09e6f875fbd1f82feed1320181cd6
Author: Hayato Ito <hayato@chromium.org>
Date: Tue Sep 18 23:28:14 2018

Enable the flag; Call capture event listeners in capturing phase at shadow hosts

This CL is a follow-up for https://chromium-review.googlesource.com/c/chromium/src/+/1212255.

It looks WebKit also landed the CL: https://trac.webkit.org/changeset/236002/webkit.

fast/dom/shadow/shadow-boundary-events.html is the only existing test which needs the rebase.

BUG= 883650 

Change-Id: Iecee6777a207b956b1dad6cc842061fd460ec6ab
Reviewed-on: https://chromium-review.googlesource.com/1229741
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592255}
[modify] https://crrev.com/47241df2c1d09e6f875fbd1f82feed1320181cd6/third_party/WebKit/LayoutTests/TestExpectations
[modify] https://crrev.com/47241df2c1d09e6f875fbd1f82feed1320181cd6/third_party/WebKit/LayoutTests/fast/dom/shadow/shadow-boundary-events-expected.txt
[modify] https://crrev.com/47241df2c1d09e6f875fbd1f82feed1320181cd6/third_party/WebKit/LayoutTests/fast/dom/shadow/shadow-boundary-events.html
[modify] https://crrev.com/47241df2c1d09e6f875fbd1f82feed1320181cd6/third_party/blink/renderer/platform/runtime_enabled_features.json5