GitLab

This CL migrates the session management part of MediaRouter.
CreateRouteRequest is not used and we are using route selection
to let CAF start sessions automatically.

Change-Id: I58d267418d9afd11f4f44520e8ca8ad94e82388b
Reviewed-on: https://chromium-review.googlesource.com/1006358Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Zhiqiang Zhang <zqzhang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569080}