Ensure invalidation of non-composited scrollbars on resize

Ensure invalidation of non-composited scrollbars on resize

When a scrollable area is resized, scrollbars will be relocated.
The original scrollbar damage logic doesn't always cover the case
because the properties of the scrollbars may be unchanged.

We could let incremental invalidation cover scrollbars, but just do
a full invalidation if there are any non-composited scrollbars because
incremental invalidation will go away with slimming paint.

BUG=430053
TEST=fast/repaint/scrollbar-invalidation-on-resize.html
TEST=fast/repaint/scrollbar-invalidation-on-resize-with-border.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185456

[Xianzhu, 2014-11-15 00:01:50]

wangxianzhu@chromium.org changed reviewers:
+ dsinclair@chromium.org, jchaffraix@chromium.org

[dsinclair, 2014-11-17 14:50:04]

The CQ bit was checked by dsinclair@chromium.org

[dsinclair, 2014-11-17 14:50:04]

lgtm

[commit-bot: I haz the power, 2014-11-17 14:50:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/726123002/1

[commit-bot: I haz the power, 2014-11-17 17:15:14]

Committed patchset #1 (id:1) as 185456