Allow filing a bug from the "Link Bug" dialog

R=ojan@chromium.org
NOTRY=true
BUG=399734

Review URL: https://codereview.chromium.org/502293003

git-svn-id: svn://svn.chromium.org/blink/trunk@182866 bbb929c8-8fbe-4397-9dbb-9b2b20218538