Removing usused smartclip APIs

Related to Blink patch https://codereview.chromium.org/259263003/
Some APIs were dependent on chromium side patch.
https://codereview.chromium.org/260623004/
Since both patches are landed, removing the redundant APIs

BUG=NONE

Review URL: https://codereview.chromium.org/346773004

git-svn-id: svn://svn.chromium.org/blink/trunk@176776 bbb929c8-8fbe-4397-9dbb-9b2b20218538