Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar constructor (patchset #5 id:80001 of https://codereview.chromium.org/2728253002/ )

Reason for revert:
Regressed scrolling performance: https://crbug.com/699705

Original issue's description:
> Remove indirection: setup scrollbar scroll layers in the scrollbar constructor
> 
> Scrollbar layers keep track of the layer id (soon: element id) that they
> actually scroll. Before this patch, scrollbar layers were constructed
> with no scroll layer id, then later updated to set the scroll layer id.
> This patch removes this indirection and directly sets the scroll layer
> in the constructor.
> 
> Removed functions:
>   VisualViewport::setScrollLayerOnScrollbars
>   WebScrollbarLayer::setScrollLayer
>   WebScrollbarLayerImpl::setScrollLayer
>   PaintedOverlayScrollbarLayer::SetScrollLayer
>   PaintedScrollbarLayer::SetScrollLayer
>   SolidColorScrollbarLayer::SetScrollLayer
> 
> BUG=693740
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2728253002
> Cr-Commit-Position: refs/heads/master@{#455105}
> Committed: https://chromium.googlesource.com/chromium/src/+/a20ad732333dc9db2b545886acd16a11abdc5842

TBR=ajuma@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=693740
Review-Url: https://codereview.chromium.org/2743653003
Cr-Commit-Position: refs/heads/master@{#455828}
Committed: https://chromium.googlesource.com/chromium/src/+/53707d796144fb0c60f081e4477b31a7adab4e6d

[pdr., 2017-03-09 17:52:05]

The CQ bit was checked by pdr@chromium.org

[pdr., 2017-03-09 17:52:06]

Created Revert of Remove indirection: setup scrollbar scroll layers in the
scrollbar constructor

[commit-bot: I haz the power, 2017-03-09 17:52:36]

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

[bokan, 2017-03-09 18:59:01]

Seems surprising this would regress performance...

[commit-bot: I haz the power, 2017-03-09 19:30:13]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1489081925454020, "parent_rev":
"671143af9d7f195bdf6b14ac96ed990ae9e852e9", "commit_rev":
"53707d796144fb0c60f081e4477b31a7adab4e6d"}

[commit-bot: I haz the power, 2017-03-09 19:30:59]

Description was changed from

==========
Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar
constructor (patchset #5 id:80001 of https://codereview.chromium.org/2728253002/
)

Reason for revert:
Regressed scrolling performance: https://crbug.com/699705

Original issue's description:
> Remove indirection: setup scrollbar scroll layers in the scrollbar constructor
> 
> Scrollbar layers keep track of the layer id (soon: element id) that they
> actually scroll. Before this patch, scrollbar layers were constructed
> with no scroll layer id, then later updated to set the scroll layer id.
> This patch removes this indirection and directly sets the scroll layer
> in the constructor.
> 
> Removed functions:
>   VisualViewport::setScrollLayerOnScrollbars
>   WebScrollbarLayer::setScrollLayer
>   WebScrollbarLayerImpl::setScrollLayer
>   PaintedOverlayScrollbarLayer::SetScrollLayer
>   PaintedScrollbarLayer::SetScrollLayer
>   SolidColorScrollbarLayer::SetScrollLayer
> 
> BUG=693740
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2728253002
> Cr-Commit-Position: refs/heads/master@{#455105}
> Committed:
https://chromium.googlesource.com/chromium/src/+/a20ad732333dc9db2b545886acd1...

TBR=ajuma@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=693740
==========

to

==========
Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar
constructor (patchset #5 id:80001 of https://codereview.chromium.org/2728253002/
)

Reason for revert:
Regressed scrolling performance: https://crbug.com/699705

Original issue's description:
> Remove indirection: setup scrollbar scroll layers in the scrollbar constructor
> 
> Scrollbar layers keep track of the layer id (soon: element id) that they
> actually scroll. Before this patch, scrollbar layers were constructed
> with no scroll layer id, then later updated to set the scroll layer id.
> This patch removes this indirection and directly sets the scroll layer
> in the constructor.
> 
> Removed functions:
>   VisualViewport::setScrollLayerOnScrollbars
>   WebScrollbarLayer::setScrollLayer
>   WebScrollbarLayerImpl::setScrollLayer
>   PaintedOverlayScrollbarLayer::SetScrollLayer
>   PaintedScrollbarLayer::SetScrollLayer
>   SolidColorScrollbarLayer::SetScrollLayer
> 
> BUG=693740
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2728253002
> Cr-Commit-Position: refs/heads/master@{#455105}
> Committed:
https://chromium.googlesource.com/chromium/src/+/a20ad732333dc9db2b545886acd1...

TBR=ajuma@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=693740

Review-Url: https://codereview.chromium.org/2743653003
Cr-Commit-Position: refs/heads/master@{#455828}
Committed:
https://chromium.googlesource.com/chromium/src/+/53707d796144fb0c60f081e4477b...
==========

[commit-bot: I haz the power, 2017-03-09 19:31:00]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/53707d796144fb0c60f081e4477b...