ViewPainter should skip painting if not inside painting subtree

ViewPainter should skip painting if not inside painting subtree

As with other layout objects, ViewPainter should respect paintInfo.paintingRoot
as well, which is used by drag & drop code to generate drag image of a single
element.

BUG=499728
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197157

[trchen, 2015-06-12 22:54:12]

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

[trchen, 2015-06-12 22:54:44]

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

[commit-bot: I haz the power, 2015-06-12 22:54:49]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179263003/1

[trchen, 2015-06-12 22:56:58]

Note: the expected image has a black background because test runner doesn't save
alpha channel to the output. It is in fact transparent pixel.

[commit-bot: I haz the power, 2015-06-13 01:52:03]

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

[commit-bot: I haz the power, 2015-06-13 01:52:04]

Dry run: This issue passed the CQ dry run.

[trchen, 2015-06-16 04:06:40]

Ding dong

[Xianzhu, 2015-06-16 04:42:55]

The CQ bit was checked by wangxianzhu@chromium.org

[Xianzhu, 2015-06-16 04:42:55]

lgtm

[commit-bot: I haz the power, 2015-06-16 04:43:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179263003/1

[commit-bot: I haz the power, 2015-06-16 06:06:21]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197157