Avoid overriding Bubble's GetAnchorRect() where possible.

Avoid overriding Bubble's GetAnchorRect() where possible.
Use the new BubbleDelegateView::set_anchor_insets() instead.
Remove redundant DCHECK, fix indent, revise comments.

BUG=none
TEST=No noticable changes (placement or otherwise).

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=152375

[msw, 2012-08-16 23:53:31]

Hey Scott, please take a look; thanks!
(Thanks Varun for adding this general functionality!)

[sky, 2012-08-20 14:04:03]

LGTM

[commit-bot: I haz the power, 2012-08-20 17:37:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/msw@chromium.org/10830366/2001

[commit-bot: I haz the power, 2012-08-20 20:01:33]

Change committed as 152375