Rewrite how paint properties are built with bg:fixed main thread scrolling

Rewrite how paint properties are built with bg:fixed main thread scrolling

Background-attachment: fixed forces main thread scrolling. The initial
paint property implementation [1] incorrectly allowed subtrees to scroll
off the main thread when an ancestor forced main thread scrolling reasons.

If there are three nested frames (A->B->C) and B has bg: fixed objects,
both B and C should have main thread reasons set (in [1], A and B would).
This patch also removes support for non-frame scrollers to change main
thread scrolling reasons for bg: fixed so that spv1 and spv2 match.

[1] https://chromium.googlesource.com/chromium/src/+/3797c08066b335c81847266d1f16dafc9b21e886

BUG=664672
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2619393002
Cr-Commit-Position: refs/heads/master@{#442413}
Committed: https://chromium.googlesource.com/chromium/src/+/0f8b383bba59a8240c646a99fb0a5b2afc995d5d

[pdr., 2017-01-09 19:42:56]

pdr@chromium.org changed reviewers:
+ chrishtr@chromium.org

[pdr., 2017-01-09 19:43:01]

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

[commit-bot: I haz the power, 2017-01-09 19:43:52]

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, 2017-01-09 21:21:21]

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

[commit-bot: I haz the power, 2017-01-09 21:21:21]

Dry run: This issue passed the CQ dry run.

[chrishtr, 2017-01-09 23:37:40]

The CQ bit was checked by chrishtr@chromium.org

[chrishtr, 2017-01-09 23:37:41]

lgtm

[commit-bot: I haz the power, 2017-01-09 23:38:59]

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, 2017-01-10 00:19:30]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1484005060766900, "parent_rev":
"cc743fb1a6128a7b24ad79bcb5b36aba36c4ab30", "commit_rev":
"0f8b383bba59a8240c646a99fb0a5b2afc995d5d"}

[commit-bot: I haz the power, 2017-01-10 00:19:55]

Description was changed from

==========
Rewrite how paint properties are built with bg:fixed main thread scrolling

Background-attachment: fixed forces main thread scrolling. The initial
paint property implementation [1] incorrectly allowed subtrees to scroll
off the main thread when an ancestor forced main thread scrolling reasons.

If there are three nested frames (A->B->C) and B has bg: fixed objects,
both B and C should have main thread reasons set (in [1], A and B would).
This patch also removes support for non-frame scrollers to change main
thread scrolling reasons for bg: fixed so that spv1 and spv2 match.

[1]
https://chromium.googlesource.com/chromium/src/+/3797c08066b335c81847266d1f16...

BUG=664672
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
Rewrite how paint properties are built with bg:fixed main thread scrolling

Background-attachment: fixed forces main thread scrolling. The initial
paint property implementation [1] incorrectly allowed subtrees to scroll
off the main thread when an ancestor forced main thread scrolling reasons.

If there are three nested frames (A->B->C) and B has bg: fixed objects,
both B and C should have main thread reasons set (in [1], A and B would).
This patch also removes support for non-frame scrollers to change main
thread scrolling reasons for bg: fixed so that spv1 and spv2 match.

[1]
https://chromium.googlesource.com/chromium/src/+/3797c08066b335c81847266d1f16...

BUG=664672
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2619393002
Cr-Commit-Position: refs/heads/master@{#442413}
Committed:
https://chromium.googlesource.com/chromium/src/+/0f8b383bba59a8240c646a99fb0a...
==========

[commit-bot: I haz the power, 2017-01-10 00:19:56]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/0f8b383bba59a8240c646a99fb0a...