Fix crash in window shutdown by accessing the Widget via a more unique property.
Fix crash in window shutdown by accessing the Widget via a more unique property.

http://crbug.com/12156
TEST=none

Review URL: http://codereview.chromium.org/118196

git-svn-id: http://src.chromium.org/svn/trunk/src@17789 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 04daa47b9bc164da4f5225402f8922db97d4ac04
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