Remove a few more odds and ends from seamless

This CL removes a few empty functions that I missed in my previous CL to remove
iframe@seamless.

Review URL: https://codereview.chromium.org/144153003

git-svn-id: svn://svn.chromium.org/blink/trunk@165885 bbb929c8-8fbe-4397-9dbb-9b2b20218538