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)

Review URL: http://codereview.chromium.org/56096

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@12874 0039d316-1c4b-4281-b951-d872f2087c98

ropik/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium