Fix double free in DeviceController (forwarder2).

This happened in an error code path rarely exercised which is why it didn't
show up very often.

BUG=332403
R=bulach@chromium.org

Review URL: https://codereview.chromium.org/132053003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244149 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244149