Make sure IPC::ChannelProxy is destroyed on the same thread it was created on.

remoting/host/desktop_session_agent.cc

Index: remoting/host/desktop_session_agent.cc
diff --git a/remoting/host/desktop_session_agent.cc b/remoting/host/desktop_session_agent.cc
index e490af1abdc082567a03b970b4ca688e83c79b51..5c028d0f13ef1ed6953360e2e454839bd38d630f 100644
--- a/remoting/host/desktop_session_agent.cc
+++ b/remoting/host/desktop_session_agent.cc
@@ -17,6 +17,7 @@
 namespace remoting {
 
 DesktopSessionAgent::~DesktopSessionAgent() {
+  DCHECK(!network_channel_);
   DCHECK(!video_capturer_);
 }
 
@@ -141,6 +142,9 @@ bool DesktopSessionAgent::Start(const base::Closure& disconnected_task,
 void DesktopSessionAgent::Stop() {
   DCHECK(caller_task_runner()->BelongsToCurrentThread());
 
+  // Make sure the channel is closed.
+  network_channel_.reset();
+
   // Stop the video capturer.
   video_capture_task_runner()->PostTask(
       FROM_HERE, base::Bind(&DesktopSessionAgent::StopVideoCapturer, this));