Resolve screen.orientation.lock() promise with undefined.

This is following the current state of the specification.

BUG=162827

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178406

Review URL: https://codereview.chromium.org/400703003

git-svn-id: svn://svn.chromium.org/blink/trunk@178433 bbb929c8-8fbe-4397-9dbb-9b2b20218538