Fix tests to ship Aura overlay scrollbars for ChromeOS

Fix tests to ship Aura overlay scrollbars for ChromeOS.

This patch disables
SitePerProcessBrowserTest.FrameOwnerPropertiesPropagationScrolling since
that test uses the difference in layout caused by a scrollbar to detect
scrollability which obviously wont work with overlay scrollbars (it's
already disabled on Android for this reason).

We also make sure that Blink's
RuntimeEnabledFetures::overlayScrollbarEnabled setting is on for all tests
that need it when the flag is flipped. BaseAudioContextTest needs to use
mock scrollbars since otherwise it runs with a production ScrollbarTheme
but the REF above gets turned on.

Finally, I've disabled the DCHECKs in the Aura scrollbar painting code that
check that overlay scrollbars aren't trying to paint scroll corners or
scrollbar tracks. This code gets tripped by Views scrollbars that aren't
yet aware of overlay scrollbars. This issue is being worked on in 657159
and doing nothing doesn't cause any problems.

BUG=307091

[bokan, 2016-11-03 23:20:00]

Description was changed from

==========
Enable overlay scrollbars RuntimeEnabledFeature

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

to

==========
Fix tests to ship Aura overlay scrollbars for ChromeOS

BUG=307091
==========

[bokan, 2016-11-04 20:36:25]

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

[commit-bot: I haz the power, 2016-11-04 20:37:48]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 20:38:26]

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

[commit-bot: I haz the power, 2016-11-04 20:39:04]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 20:58:12]

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

[commit-bot: I haz the power, 2016-11-04 20:58:45]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 21:04:49]

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

[commit-bot: I haz the power, 2016-11-04 21:05:42]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 22:49:59]

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

[commit-bot: I haz the power, 2016-11-04 22:51:41]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 23:05:11]

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

[commit-bot: I haz the power, 2016-11-04 23:05:46]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bokan, 2016-11-04 23:18:03]

Description was changed from

==========
Fix tests to ship Aura overlay scrollbars for ChromeOS

BUG=307091
==========

to

==========
Fix tests to ship Aura overlay scrollbars for ChromeOS.

This patch disables
SitePerProcessBrowserTest.FrameOwnerPropertiesPropagationScrolling since
that test uses the difference in layout caused by a scrollbar to detect
scrollability which obviously wont work with overlay scrollbars (it's
already disabled on Android for this reason).

We also make sure that Blink's
RuntimeEnabledFetures::overlayScrollbarEnabled setting is on for all tests
that need it when the flag is flipped. BaseAudioContextTest needs to use
mock scrollbars since otherwise it runs with a production ScrollbarTheme
but the REF above gets turned on.

Finally, I've disabled the DCHECKs in the Aura scrollbar painting code that
check that overlay scrollbars aren't trying to paint scroll corners or
scrollbar tracks. This code gets tripped by Views scrollbars that aren't
yet aware of overlay scrollbars. This issue is being worked on in 657159
and doing nothing doesn't cause any problems.

BUG=307091
==========

[bokan, 2016-11-04 23:18:04]

bokan@chromium.org changed reviewers:
+ estade@chromium.org

[bokan, 2016-11-04 23:20:08]

estade@, ptal.

I've kicked off a dry run on PS#7 and PS#8. #7 keeps the painting DCHECKs and
enables the flag to make sure we're not masking any Blink issues - there'll be
failures but only for the Views scrollbars. #8 removes the DCHECKs and turns off
the flag so all tests should pass there. The dependent
https://codereview.chromium.org/2480903002# will then turn the flag on once this
lands (making reverting/blaming easier).

[commit-bot: I haz the power, 2016-11-05 00:39:14]

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

[commit-bot: I haz the power, 2016-11-05 00:39:15]

Dry run: Try jobs failed on following builders:
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Evan Stade, 2016-11-05 01:13:09]

https://codereview.chromium.org/2473163002/diff/140001/ui/native_theme/native...
File ui/native_theme/native_theme_aura.cc (right):

https://codereview.chromium.org/2473163002/diff/140001/ui/native_theme/native...
ui/native_theme/native_theme_aura.cc:178: // corner but Views code currently is
unaware of Overlays. crbug.com/657159.
I don't think this is right. Native scrollbars should go on doing what they're
doing. We have to divorce the overlay-ness of content scrollbars from the
overlay-ness of native scrollbars. It's unfortunate this is not easy to do
because of how the code is structured. You could just remove this DCHECK, but
the other places that use IsOverlayScrollbarEnabled won't be as easy.

I think you'll need to modify NativeTheme::GetInstanceForWeb to return something
that's overlay-aware, and remove references to overlays in NativeThemeAura.

[Evan Stade, 2016-11-06 02:00:51]

by the way, I have a patch in the works for this.

[bokan, 2016-11-06 02:43:21]

On 2016/11/06 02:00:51, Evan Stade wrote:
> by the way, I have a patch in the works for this.

I've got https://codereview.chromium.org/2480063002 how does that look?

[Evan Stade, 2016-11-09 00:44:49]

On 2016/11/06 02:43:21, bokan wrote:
> On 2016/11/06 02:00:51, Evan Stade wrote:
> > by the way, I have a patch in the works for this.
> 
> I've got https://codereview.chromium.org/2480063002 how does that look?

this is not waiting for review and can be closed, right?