Remove obsolete AutofillPopupMenuClient code.

BUG=330077
TEST=Code compiles, Autofill popups continue to display
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/119433005

git-svn-id: svn://svn.chromium.org/blink/trunk@164263 bbb929c8-8fbe-4397-9dbb-9b2b20218538