[Android MR] Handle client connection messages

This CL migrates the logic of handling connection messages from
clients. The logic was moved from MRP to message handler to
separate all message handling from MRP.

Bug: 711860
Change-Id: I009deda26ee51a9be1d5ea0a31af6af9d3ea6605
Reviewed-on: https://chromium-review.googlesource.com/1194968
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Zhiqiang Zhang <zqzhang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587254}
5 files changed