The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8ed19ab9413002ac5912a73745b53b679778c945

commit 8ed19ab9413002ac5912a73745b53b679778c945
Author: rbpotter <rbpotter@chromium.org>
Date: Fri Aug 24 23:59:19 2018

WebUI Polymer 2 migration: Re-enable interactive_ui_tests

These tests were disabled by https://crrev.com/c/1176206 because
they were reported as flaky on debug builds. Based on the
flakiness dashboard, it appears the failures were timeouts on the
Win10 Tests x64 (dbg) bot. interactive_ui_tests is marked as
experimental on this bot due to crbug.com/840369. The
webui_polymer2_interactive_ui_tests suite is expected to have the same
behavior, so it should also be marked as experimental on this bot.

Remove the tests from the blacklist, as they should pass on other bots.

Bug: 875443
Change-Id: Ib5b3c99cf589b1ab9994346460e95ed746533ba6
Reviewed-on: https://chromium-review.googlesource.com/1187729
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586066}
[modify] https://crrev.com/8ed19ab9413002ac5912a73745b53b679778c945/testing/buildbot/chromium.win.json
[modify] https://crrev.com/8ed19ab9413002ac5912a73745b53b679778c945/testing/buildbot/filters/webui_polymer2_interactive_ui_tests.filter
[modify] https://crrev.com/8ed19ab9413002ac5912a73745b53b679778c945/testing/buildbot/test_suite_exceptions.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e55d0320c400f73fe096043555f08c2b414a0a4

commit 4e55d0320c400f73fe096043555f08c2b414a0a4
Author: dpapad <dpapad@chromium.org>
Date: Wed Sep 12 18:08:12 2018

Settings WebUI: Enable various (already passing) tests in Polymer 2.

These tests are passing, as a result of other fixes that have
already landed (with the exception of CrSettingsLanguagesPageTest which
was failing on ChromeOS and Windows).

CrSettingsLanguagesPageTest.InputMethods
CrSettingsMainPageTest.MainPage
CrSettingsRouteDynamicParametersTest.All
CrSettingsSiteDataTest.All
CrSettingsSubpageTest.All
PasswordsAndFormsBrowserTest.uiTests

Bug: 875443
Change-Id: If4e7006cab9e05ae45120b1a29a514fa4af348d4
Reviewed-on: https://chromium-review.googlesource.com/1219938
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590752}
[modify] https://crrev.com/4e55d0320c400f73fe096043555f08c2b414a0a4/chrome/browser/resources/settings/languages_page/languages_page.js
[modify] https://crrev.com/4e55d0320c400f73fe096043555f08c2b414a0a4/testing/buildbot/filters/webui_polymer2_browser_tests.filter

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2045a38da17715a664b4059a46343789a431cce7

commit 2045a38da17715a664b4059a46343789a431cce7
Author: dpapad <dpapad@chromium.org>
Date: Wed Sep 26 01:39:16 2018

Settings WebUI: Fix SettingsA11ySignOut with Polymer 2.

Bug: 875443
Change-Id: I768985724becfe5e76946723b68a9a76c8eb6052
Reviewed-on: https://chromium-review.googlesource.com/1244602
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594176}
[modify] https://crrev.com/2045a38da17715a664b4059a46343789a431cce7/chrome/test/data/webui/settings/a11y/sign_out_a11y_test.js
[modify] https://crrev.com/2045a38da17715a664b4059a46343789a431cce7/testing/buildbot/filters/webui_polymer2_browser_tests.filter

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/37eac9aac4bc503d8e1073538228c1d2c3d82f97

commit 37eac9aac4bc503d8e1073538228c1d2c3d82f97
Author: rbpotter <rbpotter@chromium.org>
Date: Wed Oct 10 03:27:43 2018

WebUI Polymer 2 Migration: Add failing tests to the filter files

An experimental CL enabling Polymer2 by default found some additional
failing tests that were missed/did not exist in the first pass. Add
them to the blacklists in the filter files.

Bug: 875443
Change-Id: I42f6167c6582d683a663e31d276d3f69162b3655
Reviewed-on: https://chromium-review.googlesource.com/c/1272799
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598203}
[modify] https://crrev.com/37eac9aac4bc503d8e1073538228c1d2c3d82f97/testing/buildbot/filters/webui_polymer2_browser_tests.filter
[modify] https://crrev.com/37eac9aac4bc503d8e1073538228c1d2c3d82f97/testing/buildbot/filters/webui_polymer2_interactive_ui_tests.filter

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f775ce87934764e493d9afcac0a43a5a93dae93b

commit f775ce87934764e493d9afcac0a43a5a93dae93b
Author: Luciano Pacheco <lucmult@chromium.org>
Date: Tue Oct 16 23:49:24 2018

Polymer2 Enable all Files app integration tests

Change filter to include all Files app integration tests, instead of
just TabIndex ones.

Test: browser_tests --gtest_filter="*FilesAppBrowserTest.*" --enable-features=WebUIPolymer2
Bug: 875443
Change-Id: I53f3532f76f3f07dc34dc1444eb5fa4d290c0732
Reviewed-on: https://chromium-review.googlesource.com/c/1282691
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600192}
[modify] https://crrev.com/f775ce87934764e493d9afcac0a43a5a93dae93b/testing/buildbot/filters/webui_polymer2_browser_tests.filter

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ec52747a5abc25a862843edca761104b3c319764

commit ec52747a5abc25a862843edca761104b3c319764
Author: Gabriel Charette <gab@chromium.org>
Date: Mon Jan 14 16:16:49 2019

[ui_controls] Unflake Send*NotifyWhenDone() on Windows

ui_controls::Send*NotifyWhenDone() can be flaky when invoked after
ui_controls::Send*() as the former can decide to notify based on
observing a yet-to-be-processed event from the latter (or even a
yet-to-be-processed event emitted by unrelated code) and thus notify too
early, resuming and testing conditions that have yet to be met.

Solution: defer the notification if the system queue has pending events
of the same type awaiting dispatch.

Note: mouse move can be repeated indefinitely during a drag, as such we
consider a mouse move complete when it hits the target regardless of
remaining mouse move messages in the queue.

@ BUG OWNERS : This might unflake many currently disabled tests. I've
CC'ed interactive_ui_tests + Windows bugs, please try to re-enable your
test after this CL if you think it might be related.

Bug:  892228 , 640996, 897801,893078,876224,875443,873110,852786,850343,848049,846695,840369,798492,756338,751031,665296,651906,499858,468660,419468,238347,131612,106489,97777,92467
Change-Id: I548856a3948ff71a145435799b4ba3e689561f14
Reviewed-on: https://chromium-review.googlesource.com/c/1392178
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622470}
[modify] https://crrev.com/ec52747a5abc25a862843edca761104b3c319764/chrome/browser/ui/views/bookmarks/bookmark_bar_view_test.cc
[modify] https://crrev.com/ec52747a5abc25a862843edca761104b3c319764/ui/base/test/ui_controls_internal_win.cc

Chrome WebUI uses Shadow DOM v0 and HTML Imports,
ChromeOS WebUI uses Shadow DOM v0 Custom Element v0 and HTML Imports.
I want Chrome not to use these APIs towards M74.

Is this issue the right place and how about scheduling?

@yoichio: The correct issue to talk about this is the parent bug https://crbug.com/738611.

TLDR;
 - Chrome and ChromeOS will be mostly on Shadow DOM v1 and Custom Elements V1 soon,
 - Except for chrome://oobe which is still unclear when it will be migrated.
 - For both Chrome and ChromeOS there is still quite a bit of work to move away from HTML imports