[Cast MRP] Implement capabilities filtering.

In addition to app availability, the CastAppDiscoveryService will now
check the required capabilities in the MediaSource against the
capabilities supported by a sink. A sink is only returned if both
conditions are satisfied.

Bug: 809249
Change-Id: I5c6f3685db44b28560c575892637117e9ad8d711
Reviewed-on: https://chromium-review.googlesource.com/1089461
Commit-Queue: Derek Cheng <imcheng@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566191}
6 files changed