[compositor-worker] root scrolling layer is associated with document scrolling element

[compositor-worker] compositor proxy can have different element ids for main and scroll layer

This is needed to allow us to correctly proxy |document.scrollingElement| and have it properly mutate transform/opacity and scroll offset. Root Frame scroll layers are
attached to the document element which is different from the actual
scrolling element.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

[majidvp, 2016-08-30 15:12:20]

Description was changed from

==========
[compositor-worker] root scrolling layer is associated with document scrolling
element

BUG=430155
==========

to

==========
[compositor-worker] root scrolling layer is associated with document scrolling
element

BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[majidvp, 2016-08-30 15:12:28]

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

[commit-bot: I haz the power, 2016-08-30 15:12:42]

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

[majidvp, 2016-08-30 15:44:49]

Description was changed from

==========
[compositor-worker] root scrolling layer is associated with document scrolling
element

BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
[compositor-worker] Associate root scrolling layer with document's scrolling
element.

Now to mutate root scroll offsets, one just needs to proxy
|document.scrollingElement|. Document is not a valid Element so proxying is not
legal.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[majidvp, 2016-08-30 15:45:35]

Description was changed from

==========
[compositor-worker] Associate root scrolling layer with document's scrolling
element.

Now to mutate root scroll offsets, one just needs to proxy
|document.scrollingElement|. Document is not a valid Element so proxying is not
legal.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
[compositor-worker] Associate root scroll layer with document's scrolling
element.

Now to mutate root scroll offsets, one just needs to proxy
|document.scrollingElement|. Document is not a valid Element so proxying is not
legal.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[majidvp, 2016-08-30 15:46:01]

majidvp@chromium.org changed reviewers:
+ vollick@chromium.org

[commit-bot: I haz the power, 2016-08-30 16:25:37]

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

[commit-bot: I haz the power, 2016-08-30 16:25:38]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[Ian Vollick, 2016-08-30 19:53:27]

On 2016/08/30 15:46:02, majidvp wrote:

Some of these failures look real, sadly.

[majidvp, 2016-09-13 15:11:54]

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

[commit-bot: I haz the power, 2016-09-13 15:12:07]

Dry run: 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, 2016-09-13 16:12:49]

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

[commit-bot: I haz the power, 2016-09-13 16:12:50]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[majidvp, 2016-09-13 18:27:27]

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

[commit-bot: I haz the power, 2016-09-13 18:28:13]

Dry run: 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, 2016-09-13 19:23:39]

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

[commit-bot: I haz the power, 2016-09-13 19:23:40]

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_...)

[majidvp, 2016-11-24 20:56:37]

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

[commit-bot: I haz the power, 2016-11-24 20:56:55]

Dry run: 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, 2016-11-24 20:58:58]

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

[commit-bot: I haz the power, 2016-11-24 20:58:59]

Dry run: Try jobs failed on following builders:
  linux_chromium_asan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[majidvp, 2017-02-22 20:57:44]

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

[commit-bot: I haz the power, 2017-02-22 20:58:44]

Dry run: 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, 2017-02-22 21:16:18]

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

[commit-bot: I haz the power, 2017-02-22 21:16:19]

Dry run: Try jobs failed on following builders:
  linux_layout_tests_slimming_paint_v2 on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_layout_te...)

[majidvp, 2017-02-24 17:16:55]

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

[commit-bot: I haz the power, 2017-02-24 17:17:14]

Dry run: 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, 2017-02-24 18:01:14]

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

[commit-bot: I haz the power, 2017-02-24 18:01:15]

Dry run: Try jobs failed on following builders:
  linux_layout_tests_slimming_paint_v2 on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_layout_te...)

[majidvp, 2017-02-24 18:38:13]

Description was changed from

==========
[compositor-worker] Associate root scroll layer with document's scrolling
element.

Now to mutate root scroll offsets, one just needs to proxy
|document.scrollingElement|. Document is not a valid Element so proxying is not
legal.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
[compositor-worker] compositor proxy can have different element ids for main and
scroll layer

This is needed to allow us to correctly proxy |document.scrollingElement| and
have it properly mutate transform/opacity and scroll offset. Root Frame scroll
layers are
attached to the document element which is different from the actual
scrolling element.


BUG=430155
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[majidvp, 2017-02-24 18:38:13]

majidvp@chromium.org changed reviewers:
+ flackr@chromium.org
- vollick@chromium.org

[majidvp, 2017-02-24 20:49:21]

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

[commit-bot: I haz the power, 2017-02-24 20:50:00]

Dry run: 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, 2017-02-24 21:27:12]

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

[commit-bot: I haz the power, 2017-02-24 21:27:13]

Dry run: Try jobs failed on following builders:
  linux_layout_tests_slimming_paint_v2 on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_layout_te...)

[majidvp, 2017-02-27 13:36:59]

flackr@ PTAL. I think we have discussed using two element Ids before to
better handle root scrolling layer case.

[flackr, 2017-03-01 16:31:27]

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Layo...
File
third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/root-scroller.html
(right):

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Layo...
third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/root-scroller.html:7:
overflow: scroll;
Why do we need to apply overflow: scroll / limit the size of the body? Looking
at the page locally it doesn't seem to change the document.scrollingElement or
the way the page scrolls, does it change something internally?

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Layo...
third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/root-scroller.html:32:
internals.settings.setPreferCompositingToLCDTextEnabled(true);
The root scroller is always composited isn't it? It seems like this shouldn't be
necessary.

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Layo...
third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/root-scroller.html:50:

nit: collapse newlines

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Sour...
File third_party/WebKit/Source/core/dom/CompositorProxy.cpp (right):

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Sour...
third_party/WebKit/Source/core/dom/CompositorProxy.cpp:127: scrollingNode =
document;
It seems like the proper fix would be for cc to set the document scrolling layer
to be the body element's scrolling layer to reflect that this scrolling layer is
the scrolling element's scrolling layer. Then we wouldn't need to have a
separate id and it would match blink's concept of the scrolling element right?

I think this would mean changing the element id for the root scrolling contents
layer to be the document.scrollingElement's id in CompositedLayerMapping.cpp

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/graphics/CompositorMutableStateTest.cpp
(right):

https://codereview.chromium.org/2292133002/diff/80001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/graphics/CompositorMutableStateTest.cpp:103:
int scrollId = 13;
To be accurate to the real implementation, isn't the scrolling layer the outer
(root) layer?