CSS Transitions: Fix flaky transition-end-event-rendering.html

CSS Transitions: Fix flaky transition-end-event-rendering.html

We force a style recalc at the start, and wait for compositor
at the end.

BUG=248938
Review-Url: https://codereview.chromium.org/2619933002
Cr-Commit-Position: refs/heads/master@{#442818}
Committed: https://chromium.googlesource.com/chromium/src/+/d6a80917e2e0bbdda7c537ec36f7acd3183d14e8

[Eric Willigers, 2017-01-10 00:11:52]

ericwilligers@chromium.org changed reviewers:
+ alancutter@chromium.org

[alancutter (OOO until 2018), 2017-01-10 08:44:50]

lgtm

[Eric Willigers, 2017-01-11 05:02:00]

The CQ bit was checked by ericwilligers@chromium.org

[commit-bot: I haz the power, 2017-01-11 05:02:36]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-11 06:05:26]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1484110920385620, "parent_rev":
"00f98a37895bba109714215198be8e99b3826cdc", "commit_rev":
"d6a80917e2e0bbdda7c537ec36f7acd3183d14e8"}

[commit-bot: I haz the power, 2017-01-11 06:06:12]

Description was changed from

==========
CSS Transitions: Fix flaky transition-end-event-rendering.html

We force a style recalc at the start, and wait for compositor
at the end.

BUG=248938
==========

to

==========
CSS Transitions: Fix flaky transition-end-event-rendering.html

We force a style recalc at the start, and wait for compositor
at the end.

BUG=248938

Review-Url: https://codereview.chromium.org/2619933002
Cr-Commit-Position: refs/heads/master@{#442818}
Committed:
https://chromium.googlesource.com/chromium/src/+/d6a80917e2e0bbdda7c537ec36f7...
==========

[commit-bot: I haz the power, 2017-01-11 06:06:13]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/d6a80917e2e0bbdda7c537ec36f7...