Remove @host @-rules.

@host @-rules was deprecated. We should remove the code from Blink.

BUG=321956

Review URL: https://codereview.chromium.org/77053006

git-svn-id: svn://svn.chromium.org/blink/trunk@162613 bbb929c8-8fbe-4397-9dbb-9b2b20218538