Access ChromotingHost::clients_ only on network thread.

remoting/host/client_session.h

Index: remoting/host/client_session.h
diff --git a/remoting/host/client_session.h b/remoting/host/client_session.h
index 07fd38792123d17e0928f2d371ac7f353a7186a7..fe67773414a1abd3aa1cc5923f7d4b528758cfde 100644
--- a/remoting/host/client_session.h
+++ b/remoting/host/client_session.h
@@ -26,8 +26,6 @@ class ClientSession : public protocol::HostStub,
                       public base::RefCountedThreadSafe<ClientSession> {
  public:
   // Callback interface for passing events to the ChromotingHost.
-  // Called only for external events, i.e. OnSessionClosed() is not
-  // called when Disconnect() is called.
   class EventHandler {
    public:
     virtual ~EventHandler() {}