Fix flaky negative-playback-rate animation test.

Fix flaky negative-playback-rate animation test.

The animation-state-changes-negative-playback-rate.html layout test
flakily fails due to floating point errors. When setting
animation.startTime to (document.timeline.currentTime + duration),
a floating point difference can sometimes cause this to be set past
the point where the animation would be finished, thus producing
an animation that was not running. This patch prevents this from
happening by setting the startTime halfway through the animation
instead of at the end.

BUG=593982
Committed: https://crrev.com/02869b24c40dbab8971b6c6fea16040deae8333b
Cr-Commit-Position: refs/heads/master@{#384422}

[suzyh_UTC10 (ex-contributor), 2016-03-31 01:14:28]

suzyh@chromium.org changed reviewers:
+ dstockwell@chromium.org

[suzyh_UTC10 (ex-contributor), 2016-03-31 01:14:33]

The CQ bit was checked by suzyh@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-03-31 01:15:13]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1843283003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1843283003/1

[suzyh_UTC10 (ex-contributor), 2016-03-31 03:09:11]

I thought I clicked the button to send this to you for review, but it doesn't
look like it :-/

[dstockwell, 2016-03-31 03:10:13]

lgtm

https://codereview.chromium.org/1843283003/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/web-animations-api/animation-state-changes-negative-playback-rate.html
(right):

https://codereview.chromium.org/1843283003/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/web-animations-api/animation-state-changes-negative-playback-rate.html:22:
animation.startTime = document.timeline.currentTime + duration/2;
Nit. spaces around binary operators.

[suzyh_UTC10 (ex-contributor), 2016-03-31 03:12:56]

On 2016/03/31 at 03:10:13, dstockwell wrote:
> lgtm
> 
>
https://codereview.chromium.org/1843283003/diff/1/third_party/WebKit/LayoutTe...
> File
third_party/WebKit/LayoutTests/web-animations-api/animation-state-changes-negative-playback-rate.html
(right):
> 
>
https://codereview.chromium.org/1843283003/diff/1/third_party/WebKit/LayoutTe...
>
third_party/WebKit/LayoutTests/web-animations-api/animation-state-changes-negative-playback-rate.html:22:
animation.startTime = document.timeline.currentTime + duration/2;
> Nit. spaces around binary operators.

Done.

[suzyh_UTC10 (ex-contributor), 2016-03-31 03:13:02]

The CQ bit was checked by suzyh@chromium.org

[suzyh_UTC10 (ex-contributor), 2016-03-31 03:13:03]

The patchset sent to the CQ was uploaded after l-g-t-m from
dstockwell@chromium.org
Link to the patchset: https://codereview.chromium.org/1843283003/#ps20001
(title: "Style fix")

[commit-bot: I haz the power, 2016-03-31 03:13:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1843283003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1843283003/20001

[commit-bot: I haz the power, 2016-03-31 03:26:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-03-31 03:27:00]

Try jobs failed on following builders:
  linux_chromium_compile_dbg_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[suzyh_UTC10 (ex-contributor), 2016-03-31 22:36:54]

The CQ bit was checked by suzyh@chromium.org

[commit-bot: I haz the power, 2016-03-31 22:37:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1843283003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1843283003/20001

[commit-bot: I haz the power, 2016-03-31 22:42:42]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-03-31 22:44:08]

Description was changed from

==========
Fix flaky negative-playback-rate animation test.

The animation-state-changes-negative-playback-rate.html layout test
flakily fails due to floating point errors. When setting
animation.startTime to (document.timeline.currentTime + duration),
a floating point difference can sometimes cause this to be set past
the point where the animation would be finished, thus producing
an animation that was not running. This patch prevents this from
happening by setting the startTime halfway through the animation
instead of at the end.

BUG=593982
==========

to

==========
Fix flaky negative-playback-rate animation test.

The animation-state-changes-negative-playback-rate.html layout test
flakily fails due to floating point errors. When setting
animation.startTime to (document.timeline.currentTime + duration),
a floating point difference can sometimes cause this to be set past
the point where the animation would be finished, thus producing
an animation that was not running. This patch prevents this from
happening by setting the startTime halfway through the animation
instead of at the end.

BUG=593982

Committed: https://crrev.com/02869b24c40dbab8971b6c6fea16040deae8333b
Cr-Commit-Position: refs/heads/master@{#384422}
==========

[commit-bot: I haz the power, 2016-03-31 22:44:09]

Patchset 2 (id:??) landed as
https://crrev.com/02869b24c40dbab8971b6c6fea16040deae8333b
Cr-Commit-Position: refs/heads/master@{#384422}