GitLab

Move MojoChannel code out of ArcBridgeHostImpl into its own file
to be shared.

Bug: 768439
Change-Id: I730ae1f498893455f3aa2e768f47893409109768
Reviewed-on: https://chromium-review.googlesource.com/1012136Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550646}