Scrollbars should get notifications from all scrollable layers up to container.

Scrollbars should get notifications from all scrollable layers up to container.

The thumb position of a scrollbar is dependant on the scroll offsets of all
scrollable layers from the scrollbar's designated scroll layer up to its
container layer. It also needs to know about geometry changes in its
scroll and container layers. This CL revises the mechanism that registers
a scrollbar to receive notifications to include all intervening scrollable
layers.

BUG=346393
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266674

[wjmaclean, 2014-04-24 18:27:27]

There are a small number of tests that are failing on this patch; I am working
on fixing these. In the meantime, I'd like to get review started on the basic
approach at least.

[aelias_OOO_until_Jul13, 2014-04-24 20:46:01]

lgtm

[wjmaclean, 2014-04-28 17:59:42]

The CQ bit was checked by wjmaclean@chromium.org

[commit-bot: I haz the power, 2014-04-28 18:02:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wjmaclean@chromium.org/254643002/20001

[commit-bot: I haz the power, 2014-04-28 18:27:44]

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

[commit-bot: I haz the power, 2014-04-28 18:27:44]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_gn_rel

[wjmaclean, 2014-04-28 18:29:33]

The CQ bit was checked by wjmaclean@chromium.org

[commit-bot: I haz the power, 2014-04-28 18:30:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wjmaclean@chromium.org/254643002/20001

[commit-bot: I haz the power, 2014-04-28 18:47:08]

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

[commit-bot: I haz the power, 2014-04-28 18:47:08]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_gn_rel

[wjmaclean, 2014-04-28 19:31:19]

The CQ bit was checked by wjmaclean@chromium.org

[commit-bot: I haz the power, 2014-04-28 19:32:15]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wjmaclean@chromium.org/254643002/20001

[commit-bot: I haz the power, 2014-04-28 22:25:20]

Change committed as 266674