Screen Orientation API: Add support for lockOrientation() / unlockOrientation()

Screen Orientation API: Add support for lockOrientation() / unlockOrientation().

The test infrastructure is currently missing to fully test the functionality.
It will be added in a follow-up patch.

R=abarth
BUG=162827
TEST=screen_orientation/lockOrientation-array-argument.html
TEST=screen_orientation/lockOrientation-bad-argument.html
TEST=screen_orientation/lockOrientation-bad-array-argument.html
TEST=screen_orientation/lockOrientation-basic.html

Review URL: https://codereview.chromium.org/171683015

git-svn-id: svn://svn.chromium.org/blink/trunk@167561 bbb929c8-8fbe-4397-9dbb-9b2b20218538