Add screen orientation information to WebScreenInfo.

That will allow us to easily pass that information to the renderer.

BUG=162827

Review URL: https://codereview.chromium.org/238183002

git-svn-id: svn://svn.chromium.org/blink/trunk@171581 bbb929c8-8fbe-4397-9dbb-9b2b20218538