Check paint offset change after updatePaintOffsetTransform

Check paint offset change after updatePaintOffsetTransform

LayoutObject::paintOffset() is the paint offset after paintOffsetTransform.
We should compare the paint offset tree builder context after
updatePaintOffsetTransform. Previously we had false-positives of paint offset
change, causing unnecessary whole subtree paint property updates.

BUG=685179
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

[Xianzhu, 2017-02-14 01:32:29]

Description was changed from

==========
Check paint offset change after updatePaintOffsetTransform

BUG=685179
==========

to

==========
Check paint offset change after updatePaintOffsetTransform

BUG=685179
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[Xianzhu, 2017-02-14 01:32:34]

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

[commit-bot: I haz the power, 2017-02-14 01:38:48]

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

[Xianzhu, 2017-02-14 01:41:53]

Description was changed from

==========
Check paint offset change after updatePaintOffsetTransform

BUG=685179
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
Check paint offset change after updatePaintOffsetTransform

LayoutObject::paintOffset() is the paint offset after paintOffsetTransform.
We should compare the paint offset tree builder context after
updatePaintOffsetTransform. Previously we had false-positives of paint offset
change, causing unnecessary whole subtree paint property updates.

BUG=685179
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[commit-bot: I haz the power, 2017-02-14 03:16:21]

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

[commit-bot: I haz the power, 2017-02-14 03:16:22]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)