DevTools: clear layers using transparent color

DevTools: clear layers using transparent color

The default layer backing is transparent.  Clearing with anything else
can interfere with compositing later.

Use transparent color instead of opaque white when clearing layers for
partial playback.

R=caseq@chromium.org,jbroman@chromium.org
BUG=607720
Committed: https://crrev.com/cdb916fa992641446848743640537454be31a56a
Cr-Commit-Position: refs/heads/master@{#399106}

[f(malita), 2016-06-08 19:01:01]

The linked bug is triggered by the top-level synthetic saveLayer we inject in
PictureSnapshot, before we even start replaying
(https://crrev.com/15996c4ff96f68c898a5582078c9728420341633).

There are other ways to avoid that problem, but this seems safest since I
suspect the opaque layer fills could cause trouble in other cases also.

[jbroman, 2016-06-08 19:06:06]

jbroman@chromium.org changed required reviewers:
+ caseq@chromium.org

[jbroman, 2016-06-08 19:06:07]

lgtm, but please wait for caseq, because I don't fully understand why this was
cleared to white (as of
https://chromium.googlesource.com/chromium/src/+/8efbea7c559fc3cf9b3ff9244457...).

[f(malita), 2016-06-09 13:05:30]

On 2016/06/08 19:06:07, jbroman wrote:
> lgtm, but please wait for caseq, because I don't fully understand why this was
> cleared to white (as of
>
https://chromium.googlesource.com/chromium/src/+/8efbea7c559fc3cf9b3ff9244457...).

Right. Caseq PTAL, thanks!

[caseq, 2016-06-09 21:44:30]

On 2016/06/09 13:05:30, f(malita) wrote:
> On 2016/06/08 19:06:07, jbroman wrote:
> > lgtm, but please wait for caseq, because I don't fully understand why this
was
> > cleared to white (as of
> >
>
https://chromium.googlesource.com/chromium/src/+/8efbea7c559fc3cf9b3ff9244457...).
> 
> Right. Caseq PTAL, thanks!

lgtm. I can't get any rational explanation why we used white originally,
transparent is a better choice by any means.

[f(malita), 2016-06-09 22:05:40]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2016-06-09 22:06:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2044643006/1

[commit-bot: I haz the power, 2016-06-10 00:08:38]

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

[commit-bot: I haz the power, 2016-06-10 00:08:39]

Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_TIMED_OUT, no build
URL)
  mac_chromium_gn_rel on tryserver.chromium.mac (JOB_TIMED_OUT, no build URL)
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_TIMED_OUT, no build URL)

[f(malita), 2016-06-10 01:36:48]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2016-06-10 01:37:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2044643006/1

[commit-bot: I haz the power, 2016-06-10 05:10:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-10 05:10:19]

CQ bit was unchecked

[commit-bot: I haz the power, 2016-06-10 05:11:33]

Description was changed from

==========
DevTools: clear layers using transparent color

The default layer backing is transparent.  Clearing with anything else
can interfere with compositing later.

Use transparent color instead of opaque white when clearing layers for
partial playback.

R=caseq@chromium.org,jbroman@chromium.org
BUG=607720
==========

to

==========
DevTools: clear layers using transparent color

The default layer backing is transparent.  Clearing with anything else
can interfere with compositing later.

Use transparent color instead of opaque white when clearing layers for
partial playback.

R=caseq@chromium.org,jbroman@chromium.org
BUG=607720

Committed: https://crrev.com/cdb916fa992641446848743640537454be31a56a
Cr-Commit-Position: refs/heads/master@{#399106}
==========

[commit-bot: I haz the power, 2016-06-10 05:11:34]

Patchset 1 (id:??) landed as
https://crrev.com/cdb916fa992641446848743640537454be31a56a
Cr-Commit-Position: refs/heads/master@{#399106}