Crash fix for the case when target tab is removed before report is sent from the feedback.
Crash fix for the case when target tab is removed before report is sent from the feedback.


BUG=chromium-os:7717
TEST=open few tabs, then open feedback page, before you submit feedback close all pther tabs. make sure
there is no crash on feedback submit.

Review URL: http://codereview.chromium.org/3772006

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@62570 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser