[MediaRouter] ScreenAvailability - part 2

Using the ScreenAvailability enum added in
https://chromium-review.googlesource.com/c/527376/ in content/browser
and chrome/browser/

BUG=723032
TEST=existing/updated tests

Change-Id: I6667f4d6237c242dfe9446cbf9e82dd30f0858ec
Reviewed-on: https://chromium-review.googlesource.com/530284
Commit-Queue: Anton Vayvod <[email protected]>
Reviewed-by: mark a. foltz <[email protected]>
Reviewed-by: Derek Cheng <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Cr-Commit-Position: refs/heads/master@{#481030}
11 files changed