[CRD iOS] Make ChromotingSession own the AudioStub

Previously AudioStub is owned by the the (Remoting|Jni)Client class and
being passed to ChromotingSession as a WeakPtr. The AudioStub is not
used after it is passed to ChromotingSession and it is a burden for the
*Client class to manage its lifetime.

This CL fixes this by making ChromotingSession own the AudioStub.

Bug: 868088
Change-Id: I067f321b3aab7110df7bb85a8b8c519ea889865e
Reviewed-on: https://chromium-review.googlesource.com/1171840
Reviewed-by: Joe Downing <joedow@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582428}
7 files changed