Propagate connection state from networking layer to UI.

remoting/protocol/session.h

Index: remoting/protocol/session.h
diff --git a/remoting/protocol/session.h b/remoting/protocol/session.h
index 9345b3053622e6585e75b651d750b6e79cb996f9..eaf18d3f664333b19f00faa2e9c03f015c56b3e3 100644
--- a/remoting/protocol/session.h
+++ b/remoting/protocol/session.h
@@ -70,6 +70,10 @@ class Session : public base::NonThreadSafe {
     // |channel_name| changes.
     virtual void OnSessionRouteChange(const std::string& channel_name,
                                       const TransportRoute& route) = 0;
+
+    // Called when inactive state on one of the channels changes.
+    virtual void OnSessionInactive(const std::string& channel_name,
+                                   bool inactive) {}
   };
 
   // TODO(sergeyu): Specify connection error code when channel