The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/823ec06c330538e88cf641061ea42cd607254e57

commit 823ec06c330538e88cf641061ea42cd607254e57
Author: jcivelli <jcivelli@chromium.org>
Date: Wed Mar 01 03:13:49 2017

Adding a new message type to the Mojo channel.

Adding a new Channel::Message type and changing Channel so it
supports the old and the new messages.
This will help when modules using different version of Mojo
communicate.

BUG= 695510 

Review-Url: https://codereview.chromium.org/2710193003
Cr-Commit-Position: refs/heads/master@{#453814}

[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/BUILD.gn
[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/broker_messages.h
[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/channel.cc
[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/channel.h
[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/channel_posix.cc
[add] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/channel_unittest.cc
[modify] https://crrev.com/823ec06c330538e88cf641061ea42cd607254e57/mojo/edk/system/node_channel.cc