Update ICE protocol to handle closed channel

An ICE/PseudoTcp channel may be closed by the peer. Read() may returns 0
in that case. MessageReader wasn't expecting 0 and was DCHECK'ing in that
case. Also update StreamMessagePipeAdapter to handle this case as closed
MessagePipe.

BUG=700167

Review-Url: https://codereview.chromium.org/2757723002
Cr-Commit-Position: refs/heads/master@{#457842}
11 files changed