Revert accidental rename of X-Frame-Options.

This was rewritten to X-LocalFrame-Options in r167851. Oops.

BUG=none
TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/181063003

git-svn-id: svn://svn.chromium.org/blink/trunk@167854 bbb929c8-8fbe-4397-9dbb-9b2b20218538