Fire accessible event on web area object when scrolling

Fire accessible event on web area object when scrolling

Scroll events for the main document were accidentally removed in bug
371039 - this is a better way to restore them by firing them on the
web area, rather than the ScrollView/FrameView.

This brings back the "scroll" sounds on Android, and also makes Android
update the position of accessibility focus after scrolling.

BUG=371039, 374316, 414291
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184002

[dmazzoni, 2014-10-17 23:07:59]

dmazzoni@chromium.org changed reviewers:
+ aboxhall@chromium.org

[aboxhall, 2014-10-20 15:10:50]

lgtm

[dmazzoni, 2014-10-20 15:25:42]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-10-20 15:26:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/662913002/1

[commit-bot: I haz the power, 2014-10-20 16:24:32]

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

[commit-bot: I haz the power, 2014-10-20 16:24:33]

Try jobs failed on following builders:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/2...)

[dmazzoni, 2014-10-20 17:37:22]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-10-20 17:38:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/662913002/20001

[commit-bot: I haz the power, 2014-10-20 18:52:54]

Committed patchset #2 (id:20001) as 184002