Clip Scrollbar painting like contents painting in ScrollView

Clip Scrollbar painting like contents painting in ScrollView

Previously, it was possible to paint a scroll corner that was larger
than the iframe it was attached to, effectively enabling it to paint
over parts of the parent frame. This change clips scrollbar painting
the same way we clip contents.

BUG=331168
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170625

[esprehn, 2014-04-01 23:39:42]

lgtm, crazy bug

[leviw_travelin_and_unemployed, 2014-04-01 23:41:43]

The CQ bit was checked by leviw@chromium.org

[commit-bot: I haz the power, 2014-04-01 23:41:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/leviw@chromium.org/220243010/1

[commit-bot: I haz the power, 2014-04-02 00:42:04]

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

[commit-bot: I haz the power, 2014-04-02 00:42:04]

Try jobs failed on following builders:
  tryserver.blink on linux_blink_dbg

[leviw_travelin_and_unemployed, 2014-04-02 01:09:35]

The CQ bit was checked by leviw@chromium.org

[commit-bot: I haz the power, 2014-04-02 01:09:39]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/leviw@chromium.org/220243010/1

[commit-bot: I haz the power, 2014-04-02 02:15:28]

Change committed as 170625