Changes in PaintLayer and PaintLayerPainter for synchronized painting

Changes in PaintLayer and PaintLayerPainter for synchronized painting

- Simplify ancestor marking of needsRepaint flags, because we have
  synchronzied whole layer-tree cleaning of the flags after painting.
  This removes the dependency of needs repaint flag to self-painting
  flag.

- Don't output subsequence for non-self-painting layers. Previously
  we output subsequence for non-self-painting layers which has
  self-painting descendants. This reduces number of subsequences.

- Don't output subsequences when printing because they are no use.

- Don't output subsequence when painting overlay scrollbars to avoid
  duplicated display item ids and another tree of subsequences which
  just enclose overlay scrollbars.

Covered by existing tests when synchronized painting is enabled.

BUG=536999
Committed: https://crrev.com/5c2c5188dcc571c2a14ac424d7ade336ef99971a
Cr-Commit-Position: refs/heads/master@{#357007}

[Xianzhu, 2015-10-29 23:07:02]

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

[chrishtr, 2015-10-29 23:11:54]

The CQ bit was checked by chrishtr@chromium.org

[chrishtr, 2015-10-29 23:11:54]

lgtm

[commit-bot: I haz the power, 2015-10-29 23:13:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1424933004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1424933004/1

[commit-bot: I haz the power, 2015-10-30 01:19:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-30 01:19:58]

Patchset 1 (id:??) landed as
https://crrev.com/5c2c5188dcc571c2a14ac424d7ade336ef99971a
Cr-Commit-Position: refs/heads/master@{#357007}