Fix a browser crash that occurs if the extension unpacker process crashes after it sends a response to the browser.
Fix a browser crash that occurs if the extension unpacker process crashes
after it sends a response to the browser.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/113867

git-svn-id: http://src.chromium.org/svn/trunk/src@17222 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 0aa0f614bfb58fd68f72a35f8460b728fe2e054b
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