[chrome-devtools-frontend] Add new exit code Forgot to include into the previous change [email protected],[email protected] Review URL: https://codereview.chromium.org/1351383003 . git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/chrome-devtools-frontend@296770 0039d316-1c4b-4281-b951-d872f2087c98