Fix a crash when closing a window with a download animation.
Fix a crash when closing a window with a download animation.

This CL fixes a crash that occurs when a small download has
completed quickly, and the download shelf receives two 'complete'
notifications (one at shelf item creation, and one when the
download observer fires).

We detect this case by checking for an existing complete
animation and ignoring the second notification.

BUG=18416 (http://crbug.com/18416)
TEST=Download something, close the window before the animation completes
     and notice that Chrome doesn't crash.

Review URL: http://codereview.chromium.org/174326

git-svn-id: http://src.chromium.org/svn/trunk/src@24131 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: e8a84f596040786e6fc99a07f2b120d57b9d4ac7
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser