UMA histogram to measure the time OTS takes to decode a webfont

UMA histogram to measure the time OTS takes to decode a webfont

This adds WebFont.DecodeSpeed.* histograms that record the rate at which
OTS decodes a webfont to uncompressed format.

BUG=447127
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188440

[Kunihiko Sakamoto, 2015-01-14 01:28:13]

ksakamoto@chromium.org changed reviewers:
+ bashi@chromium.org, eae@chromium.org

[bashi, 2015-01-14 01:46:29]

Have you tried to measure the metrics? I'd like to confirm that this will
provide useful values (In other words, will kB/sec be a suitable unit for
typical web fonts?).

[Kunihiko Sakamoto, 2015-01-14 04:17:34]

On 2015/01/14 01:46:29, bashi1 wrote:
> Have you tried to measure the metrics? I'd like to confirm that this will
> provide useful values (In other words, will kB/sec be a suitable unit for
> typical web fonts?).

Thanks for checking. I was only testing it on debug builds and the max bucket
was too small.
I've changed the max bucket size from 100MB/s to 500MB/s.

On my Z620 w/ release build,
* SFNT: ~150MB/s
* WOFF: ~80MB/s
* WOFF2: ~30MB/s

On Nexus 4 w/ release build:
* WOFF: ~13MB/s

Since WOFF2 + low end devices can be very slow, I think it's good to have
sub-MB/s resolution.
WDYT?

[bashi, 2015-01-14 04:32:18]

On 2015/01/14 04:17:34, Kunihiko Sakamoto wrote:
> On 2015/01/14 01:46:29, bashi1 wrote:
> > Have you tried to measure the metrics? I'd like to confirm that this will
> > provide useful values (In other words, will kB/sec be a suitable unit for
> > typical web fonts?).
> 
> Thanks for checking. I was only testing it on debug builds and the max bucket
> was too small.
> I've changed the max bucket size from 100MB/s to 500MB/s.
> 
> On my Z620 w/ release build,
> * SFNT: ~150MB/s
> * WOFF: ~80MB/s
> * WOFF2: ~30MB/s
> 
> On Nexus 4 w/ release build:
> * WOFF: ~13MB/s
> 
> Since WOFF2 + low end devices can be very slow, I think it's good to have
> sub-MB/s resolution.
> WDYT?

Thank you for checking! non-owner LGTM.

[eae, 2015-01-14 17:50:23]

LGTM

[Kunihiko Sakamoto, 2015-01-15 02:24:58]

The CQ bit was checked by ksakamoto@chromium.org

[commit-bot: I haz the power, 2015-01-15 02:26:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/842913004/20001

[commit-bot: I haz the power, 2015-01-15 03:38:56]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188440