RootLayerScrolling: Fix RootScrollerTest.

RootLayerScrolling: Fix RootScrollerTest.

When RLS is enabled, the compositor's root content layer is pointless,
and it doesn't get its setMasksToBounds flag set based on whether it
contains the root scroller.

Instead, we should ensure that the LayoutView's scrolling layer gets
the setMasksToBounds flag set correctly.  This patch adds some spacers
to make the LayoutView overflow, to ensure that it has a scrolling
layer we can test.

BUG=490942
R=bokan@chromium.org,skobes@chromium.org

Committed: https://crrev.com/fcf5015deccb246d2dca3c8037db8b6c8a234547
Cr-Commit-Position: refs/heads/master@{#438727}

[skobes, 2016-12-15 01:59:28]

lgtm

[szager1, 2016-12-15 02:04:16]

The CQ bit was checked by szager@chromium.org

[commit-bot: I haz the power, 2016-12-15 02:04:25]

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, 2016-12-15 02:11:56]

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

[commit-bot: I haz the power, 2016-12-15 02:11:56]

Try jobs failed on following builders:
  win_clang on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/...)

[szager1, 2016-12-15 02:55:30]

The CQ bit was checked by szager@chromium.org

[commit-bot: I haz the power, 2016-12-15 02:55:47]

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, 2016-12-15 03:56:14]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1481770530279190, "parent_rev":
"258e69d91a67ac80468660a7d85510a717e44a7e", "commit_rev":
"079bc9a7e410e82940fac2fe488df1d0361395bb"}

[commit-bot: I haz the power, 2016-12-15 03:56:44]

Description was changed from

==========
RootLayerScrolling: Fix RootScrollerTest.

When RLS is enabled, the compositor's root content layer is pointless,
and it doesn't get its setMasksToBounds flag set based on whether it
contains the root scroller.

Instead, we should ensure that the LayoutView's scrolling layer gets
the setMasksToBounds flag set correctly.  This patch adds some spacers
to make the LayoutView overflow, to ensure that it has a scrolling
layer we can test.

BUG=490942
R=bokan@chromium.org,skobes@chromium.org
==========

to

==========
RootLayerScrolling: Fix RootScrollerTest.

When RLS is enabled, the compositor's root content layer is pointless,
and it doesn't get its setMasksToBounds flag set based on whether it
contains the root scroller.

Instead, we should ensure that the LayoutView's scrolling layer gets
the setMasksToBounds flag set correctly.  This patch adds some spacers
to make the LayoutView overflow, to ensure that it has a scrolling
layer we can test.

BUG=490942
R=bokan@chromium.org,skobes@chromium.org

Review-Url: https://codereview.chromium.org/2576943002
==========

[commit-bot: I haz the power, 2016-12-15 03:56:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-12-15 04:00:52]

Description was changed from

==========
RootLayerScrolling: Fix RootScrollerTest.

When RLS is enabled, the compositor's root content layer is pointless,
and it doesn't get its setMasksToBounds flag set based on whether it
contains the root scroller.

Instead, we should ensure that the LayoutView's scrolling layer gets
the setMasksToBounds flag set correctly.  This patch adds some spacers
to make the LayoutView overflow, to ensure that it has a scrolling
layer we can test.

BUG=490942
R=bokan@chromium.org,skobes@chromium.org

Review-Url: https://codereview.chromium.org/2576943002
==========

to

==========
RootLayerScrolling: Fix RootScrollerTest.

When RLS is enabled, the compositor's root content layer is pointless,
and it doesn't get its setMasksToBounds flag set based on whether it
contains the root scroller.

Instead, we should ensure that the LayoutView's scrolling layer gets
the setMasksToBounds flag set correctly.  This patch adds some spacers
to make the LayoutView overflow, to ensure that it has a scrolling
layer we can test.

BUG=490942
R=bokan@chromium.org,skobes@chromium.org

Committed: https://crrev.com/fcf5015deccb246d2dca3c8037db8b6c8a234547
Cr-Commit-Position: refs/heads/master@{#438727}
==========

[commit-bot: I haz the power, 2016-12-15 04:00:53]

Patchset 1 (id:??) landed as
https://crrev.com/fcf5015deccb246d2dca3c8037db8b6c8a234547
Cr-Commit-Position: refs/heads/master@{#438727}

[bokan, 2016-12-15 15:28:20]

what problem was this causing? What happens in real pages where there is no
scrolling in the LayoutView?

[szager1, 2016-12-15 15:50:49]

On 2016/12/15 15:28:20, bokan wrote:
> what problem was this causing? What happens in real pages where there is no
> scrolling in the LayoutView?

The purpose of this patch is just to get the unit tests passing with root layer
scrolling enabled; it only touches test code.

[bokan, 2016-12-15 15:51:28]

On 2016/12/15 15:50:49, szager1 wrote:
> On 2016/12/15 15:28:20, bokan wrote:
> > what problem was this causing? What happens in real pages where there is no
> > scrolling in the LayoutView?
> 
> The purpose of this patch is just to get the unit tests passing with root
layer
> scrolling enabled; it only touches test code.

Right, I meant why were the tests failing?

[szager1, 2016-12-16 00:52:16]

On 2016/12/15 15:51:28, bokan wrote:
> On 2016/12/15 15:50:49, szager1 wrote:
> > On 2016/12/15 15:28:20, bokan wrote:
> > > what problem was this causing? What happens in real pages where there is
no
> > > scrolling in the LayoutView?
> > 
> > The purpose of this patch is just to get the unit tests passing with root
> layer
> > scrolling enabled; it only touches test code.
> 
> Right, I meant why were the tests failing?

They were failing because of this line of code:

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/layout/co...

I could have just disabled the test assertion for that line, but I thought it
would be useful to test that setMasksToBounds is applied correctly to the
LayoutView's scrolling layer:

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/layout/co...

I had to add spacers to the html to force root-layer scrolling, because without
it, the LayoutView's CompositedLayerMapping would not have a scrollLayer.