Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

The main thread case still needs to be fixed.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2863103002
Cr-Commit-Position: refs/heads/master@{#472542}
Committed: https://chromium.googlesource.com/chromium/src/+/7fe8085f9f4f10d88ec704588adea49392303fbe

[tdresser, 2017-05-05 13:24:12]

Description was changed from

==========
Reduce smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

BUG=599910, 717652
==========

to

==========
Reduce smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

[tdresser, 2017-05-05 13:24:55]

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

[commit-bot: I haz the power, 2017-05-05 13:25:11]

Dry run: CQ is trying da patch.

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

[tdresser, 2017-05-05 13:29:04]

Description was changed from

==========
Reduce smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

to

==========
Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

The main thread case still needs to be fixed.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

[commit-bot: I haz the power, 2017-05-05 13:39:28]

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

[commit-bot: I haz the power, 2017-05-05 13:39:29]

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

[tdresser, 2017-05-15 18:24:01]

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

[commit-bot: I haz the power, 2017-05-15 18:24:55]

Dry run: 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, 2017-05-15 19:36:09]

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

[commit-bot: I haz the power, 2017-05-15 19:36:10]

Dry run: Try jobs failed on following builders:
  win_clang on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/...)

[tdresser, 2017-05-16 21:05:11]

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

[commit-bot: I haz the power, 2017-05-16 21:06:42]

Dry run: 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, 2017-05-16 22:54:56]

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

[commit-bot: I haz the power, 2017-05-16 22:54:56]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[tdresser, 2017-05-17 12:08:08]

tdresser@chromium.org changed reviewers:
+ ajuma@chromium.org, skobes@chromium.org

[tdresser, 2017-05-17 12:08:08]

+ajuma@ for CC.
+skobes@ for smooth scroll changes.

[ajuma, 2017-05-17 13:17:04]

cc lgtm with a question:

Now that we're starting the animation part-way through, I wonder if we should
adjust the duration so that the actual duration is the same as before. skobes@,
wdyt?

[skobes, 2017-05-17 15:35:04]

lgtm

This will start one frame in, and finish one frame sooner, right?  I think we
shouldn't adjust the duration - if the first frame had zero delta then the
"true" duration hasn't actually changed.

[tdresser, 2017-05-17 16:04:40]

On 2017/05/17 15:35:04, skobes wrote:
> lgtm
> 
> This will start one frame in, and finish one frame sooner, right?  I think we
> shouldn't adjust the duration - if the first frame had zero delta then the
> "true" duration hasn't actually changed.

Yup, I believe that's the case.

Thanks.

[tdresser, 2017-05-17 16:04:45]

The CQ bit was checked by tdresser@chromium.org

[commit-bot: I haz the power, 2017-05-17 16:05:22]

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, 2017-05-17 19:57:54]

CQ is committing da patch.

Bot data: {"patchset_id": 60001, "attempt_start_ts": 1495037085469870,
"parent_rev": "c29cc4ea75913bb687853ef0722ca45084c72a61", "commit_rev":
"7fe8085f9f4f10d88ec704588adea49392303fbe"}

[commit-bot: I haz the power, 2017-05-17 19:58:04]

Description was changed from

==========
Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

The main thread case still needs to be fixed.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

to

==========
Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

Previously input which triggered a smooth scroll didn't scroll
at all on the first frame of the smooth scroll animation.

This introduced unnecessary latency, and also prevented out input
latency instrumentation from realizing that the input produced a
frame.

This removes that latency by starting the animation one frame in,
and causes our input latency pipeline to recognize that this input
triggered a frame being drawn.

The main thread case still needs to be fixed.

BUG=599910, 717652
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2863103002
Cr-Commit-Position: refs/heads/master@{#472542}
Committed:
https://chromium.googlesource.com/chromium/src/+/7fe8085f9f4f10d88ec704588ade...
==========

[commit-bot: I haz the power, 2017-05-17 19:58:05]

Committed patchset #4 (id:60001) as
https://chromium.googlesource.com/chromium/src/+/7fe8085f9f4f10d88ec704588ade...