cc : Initialize solid color scrollbar layer on main thread to 0.

cc : Initialize solid color scrollbar layer on main thread to 0.

We currently initialize it to 0 on the compositor thread. This is
required to make property trees on the compositor thread independent of
opacity stored on LayerImpl (with the goal of deleting
LayerImpl::opacity)

BUG=609205
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/3093be3ace64cb9049fd76ccbcc749e2a48cd58d
Cr-Commit-Position: refs/heads/master@{#395959}

[jaydasika, 2016-05-20 22:38:30]

Description was changed from

==========
cc : Initialize solid color scrollbar layer on main thread to 0.

We currently initialize it to 0 on the compositor thread. This is
required to make property trees on the compositor thread independent of
opacity stored on LayerImpl (with the goal of deleting
LayerImpl::opacity)

BUG=609205
==========

to

==========
cc : Initialize solid color scrollbar layer on main thread to 0.

We currently initialize it to 0 on the compositor thread. This is
required to make property trees on the compositor thread independent of
opacity stored on LayerImpl (with the goal of deleting
LayerImpl::opacity)

BUG=609205
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
==========

[jaydasika, 2016-05-20 22:43:11]

jaydasika@chromium.org changed reviewers:
+ ajuma@chromium.org, enne@chromium.org, vollick@chromium.org

[jaydasika, 2016-05-20 22:43:12]

PTAL

[jaydasika, 2016-05-20 22:46:33]

https://codereview.chromium.org/1999783003/diff/1/cc/layers/scrollbar_layer_u...
File cc/layers/scrollbar_layer_unittest.cc (right):

https://codereview.chromium.org/1999783003/diff/1/cc/layers/scrollbar_layer_u...
cc/layers/scrollbar_layer_unittest.cc:550: EXPECT_EQ(node->data.opacity, 0.f);
This tests that 0 opacity gets pushed onto the active tree.

[jaydasika, 2016-05-20 23:49:44]

jaydasika@chromium.org changed reviewers:
+ aelias@chromium.org

[jaydasika, 2016-05-20 23:49:44]

+aelias
Ali pointed out in an offline discussion that we need to prevent blink from
changing the initial opacity(0) before it gets pushed so that the initialization
on impl happens correctly. So, I have initialized the opacity of the scrollbar
to 0 on main thread and made a override of SetOpacity so that it can never be
changed by blink.

[aelias_OOO_until_Jul13, 2016-05-21 00:14:10]

Semantic change is fine by me, but wouldn't it be cleaner to change Blink to
always set the value to zero, instead of overriding Blink's decision here?

[jaydasika, 2016-05-24 23:37:23]

It looks like blink ensures it sets up scrollbars with 0 opacity already (See
VisualViewport::setupScrollbar)

https://codereview.chromium.org/1999783003/diff/60001/cc/layers/solid_color_s...
File cc/layers/solid_color_scrollbar_layer.cc (right):

https://codereview.chromium.org/1999783003/diff/60001/cc/layers/solid_color_s...
cc/layers/solid_color_scrollbar_layer.cc:61: DCHECK_EQ(opacity, 0.f);
I am not sure if we should still be overriding this function, but it seems safe
to do it? Wdyt ?

[aelias_OOO_until_Jul13, 2016-05-24 23:47:14]

lgtm

[jaydasika, 2016-05-25 18:41:32]

The CQ bit was checked by jaydasika@chromium.org

[commit-bot: I haz the power, 2016-05-25 18:41:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1999783003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1999783003/60001

[commit-bot: I haz the power, 2016-05-25 19:24:07]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-05-25 19:25:34]

Description was changed from

==========
cc : Initialize solid color scrollbar layer on main thread to 0.

We currently initialize it to 0 on the compositor thread. This is
required to make property trees on the compositor thread independent of
opacity stored on LayerImpl (with the goal of deleting
LayerImpl::opacity)

BUG=609205
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
==========

to

==========
cc : Initialize solid color scrollbar layer on main thread to 0.

We currently initialize it to 0 on the compositor thread. This is
required to make property trees on the compositor thread independent of
opacity stored on LayerImpl (with the goal of deleting
LayerImpl::opacity)

BUG=609205
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/3093be3ace64cb9049fd76ccbcc749e2a48cd58d
Cr-Commit-Position: refs/heads/master@{#395959}
==========

[commit-bot: I haz the power, 2016-05-25 19:25:35]

Patchset 4 (id:??) landed as
https://crrev.com/3093be3ace64cb9049fd76ccbcc749e2a48cd58d
Cr-Commit-Position: refs/heads/master@{#395959}