Unbreak max scroll offset in threaded compositing mode.

Unbreak max scroll offset in threaded compositing mode.

This was broken by a cleanup in
https://src.chromium.org/viewvc/chrome?view=rev&revision=177847.
Reverting that part of the patch.

TBR=enne
NOTRY=true
BUG=171188
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=177886

[aelias_OOO_until_Jul13, 2013-01-21 01:52:30]

Hi, I think we should revert this until the WebKit issue is fixed.

[enne (OOO), 2013-01-21 02:08:44]

What's the WebKit issue?

[enne (OOO), 2013-01-21 02:10:10]

Oh, sorry.  I see the bug you filed.  This lgtm.

[aelias_OOO_until_Jul13, 2013-01-21 02:12:14]

root scroll layer bounds are sometimes (0,0).  I assume this is because
ScrollingCoordinatorChromium::frameViewLayoutUpdated is not called when
expected, or the layer tree is not fully constructed when it's called.

Note that the original change also broke scrolling in non-CSS-transform page
scale mode on Android since it was landed before
https://chromiumcodereview.appspot.com/11958004/ .

[commit-bot: I haz the power, 2013-01-21 02:13:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/aelias@chromium.org/12034003/1

[commit-bot: I haz the power, 2013-01-21 02:19:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/aelias@chromium.org/12034003/1

[commit-bot: I haz the power, 2013-01-21 03:21:05]

Change committed as 177886