Update xulrunner to include README.chromium for licensing attribution.
Update xulrunner to include README.chromium for licensing attribution.

BUG=None.
TEST=None.
Review URL: http://codereview.chromium.org/6246130

git-svn-id: http://src.chromium.org/svn/trunk/src@73920 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 73bddc57cddeb9e27ace37da44b63e307f63daff
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