Fix off-by-one in fps_meter, fix unit test to catch this.

Fix off-by-one in fps_meter, fix unit test to catch this.

The FPS counter returned bogus negative values as soon as the
sample count reached kNumFrameTimes since it subtracted a zero value
that was never set due to an off-by-one error.

Unfortunately the unit test didn't catch this since it never filled
the sample buffer. Fixed the test to cover this.

Also reduce kNumFrameTimes to 10, smoothing over 200 frames seems
excessive. We just want a bit of smoothing but should be able to
see some reaction to temporary glitches since these are quite visible
in VR.

BUG=

Review-Url: https://codereview.chromium.org/2892813002
Cr-Commit-Position: refs/heads/master@{#473810}
Committed: https://chromium.googlesource.com/chromium/src/+/c90c34417bb295752d1e7fa96ba5d41c106917fd

[klausw, 2017-05-18 18:38:54]

klausw@chromium.org changed reviewers:
+ cjgrant@chromium.org, vollick@chromium.org

[klausw, 2017-05-18 18:38:54]

FYI, I ran into this issue while adding debug output for the FPS meter.

[klausw, 2017-05-18 18:58:35]

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

[commit-bot: I haz the power, 2017-05-18 18:59:33]

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, 2017-05-18 20:12:49]

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

[commit-bot: I haz the power, 2017-05-18 20:12:49]

Dry run: This issue passed the CQ dry run.

[klausw, 2017-05-22 20:51:37]

On 2017/05/18 18:38:54, klausw wrote:
> FYI, I ran into this issue while adding debug output for the FPS meter.

Ping? Still waiting for review of this one. I've been using the FPS meter in
test builds, and it would make life easier to have this work at ToT to avoid
having to patch this in manually.

[Ian Vollick, 2017-05-22 22:33:59]

On 2017/05/22 20:51:37, klausw wrote:
> On 2017/05/18 18:38:54, klausw wrote:
> > FYI, I ran into this issue while adding debug output for the FPS meter.
> 
> Ping? Still waiting for review of this one. I've been using the FPS meter in
> test builds, and it would make life easier to have this work at ToT to avoid
> having to patch this in manually.

lgtm

[klausw, 2017-05-22 23:59:17]

The CQ bit was checked by klausw@chromium.org

[commit-bot: I haz the power, 2017-05-22 23:59:57]

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, 2017-05-23 00:10:40]

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

[commit-bot: I haz the power, 2017-05-23 00:10:41]

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

[klausw, 2017-05-23 01:19:58]

On 2017/05/23 00:10:41, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

@cjgrant or others, looks like I still need OWNERS approval?

[mthiesse, 2017-05-23 04:29:50]

mthiesse@chromium.org changed reviewers:
+ mthiesse@chromium.org

[mthiesse, 2017-05-23 04:29:50]

lgtm

[mthiesse, 2017-05-23 04:30:07]

The CQ bit was checked by mthiesse@chromium.org

[commit-bot: I haz the power, 2017-05-23 04:30:19]

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, 2017-05-23 04:34:55]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1495513807695950, "parent_rev":
"26fe0dac88cb99bc94ce4d5f1ed9bc6cfff2f88e", "commit_rev":
"c90c34417bb295752d1e7fa96ba5d41c106917fd"}

[commit-bot: I haz the power, 2017-05-23 04:35:07]

Description was changed from

==========
Fix off-by-one in fps_meter, fix unit test to catch this.

The FPS counter returned bogus negative values as soon as the
sample count reached kNumFrameTimes since it subtracted a zero value
that was never set due to an off-by-one error.

Unfortunately the unit test didn't catch this since it never filled
the sample buffer. Fixed the test to cover this.

Also reduce kNumFrameTimes to 10, smoothing over 200 frames seems
excessive. We just want a bit of smoothing but should be able to
see some reaction to temporary glitches since these are quite visible
in VR.

BUG=
==========

to

==========
Fix off-by-one in fps_meter, fix unit test to catch this.

The FPS counter returned bogus negative values as soon as the
sample count reached kNumFrameTimes since it subtracted a zero value
that was never set due to an off-by-one error.

Unfortunately the unit test didn't catch this since it never filled
the sample buffer. Fixed the test to cover this.

Also reduce kNumFrameTimes to 10, smoothing over 200 frames seems
excessive. We just want a bit of smoothing but should be able to
see some reaction to temporary glitches since these are quite visible
in VR.

BUG=

Review-Url: https://codereview.chromium.org/2892813002
Cr-Commit-Position: refs/heads/master@{#473810}
Committed:
https://chromium.googlesource.com/chromium/src/+/c90c34417bb295752d1e7fa96ba5...
==========

[commit-bot: I haz the power, 2017-05-23 04:35:10]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/c90c34417bb295752d1e7fa96ba5...