Change web notifications to show at the top of the list, clean up layout.

Change web notifications to show at the top of the list, clean up layout.

This partially addresses http://code.google.com/p/chromium/issues/detail?id=137155 by placing new notifications at the front of the list and rendering newer notifications first.
This also greatly simplifes the layout code for web notifications.
It also fixes a bug where notifications were not getting redrawn correctly when the shelf alignment was changed.

BUG=137155
TEST=New web notifications should show up at the top of the list. The list should size correctly as new notifications arrive, scrolling when the max size is reached, showing up to 99 notifications in the list.
R=sadrul@chromium.org


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=148991

[stevenjb, 2012-07-26 22:59:50]

Ready for review. Please take a quick look if you can, I would like to rebase
http://codereview.chromium.org/10808066/ with these changes and update it for
review.

[sadrul, 2012-07-27 20:36:03]

LGTM (sorry about the delay. fell through the cracks)

[commit-bot: I haz the power, 2012-07-30 17:21:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/stevenjb@chromium.org/10833041/1

[commit-bot: I haz the power, 2012-07-30 18:54:20]

Change committed as 148991