Properly Remove Autofill Keyboard Listener.

Remove the keyboard listener before we implicitly delete the object. Also
update the removal code to catch problems like this if they occur again.

R=estade@chromium.org
BUG=175454


Review URL: https://chromiumcodereview.appspot.com/12223106

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182751 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed