Delete downloads after updating observers....

Delete downloads after updating observers.

The download page adds itself as an observer to in-progress
and unconfirmed dangerous downloads, and removes itself when
the download manager indicates its state has changed.

This caused a crash when the downloads were deleted during a
"clear browsing data" operation, since the delete happened
before the download page was notified of a download manager
state change. The download page then attempted to remove itself
from a deleted item.

BUG=9444
(http://crbug.com/9444)


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=12874