Adding ThreadChecker validation to d'tors for protocol classes

remoting/protocol/webrtc_connection_to_client.cc

Index: remoting/protocol/webrtc_connection_to_client.cc
diff --git a/remoting/protocol/webrtc_connection_to_client.cc b/remoting/protocol/webrtc_connection_to_client.cc
index 60f02823a1acd68fa951e6a9366e9c5f30b5fcc5..a6fdc5b34d1725506b00453c8bf04b1ce25ec25b 100644
--- a/remoting/protocol/webrtc_connection_to_client.cc
+++ b/remoting/protocol/webrtc_connection_to_client.cc
@@ -54,7 +54,9 @@ WebrtcConnectionToClient::WebrtcConnectionToClient(
   session_->SetTransport(transport_.get());
 }
 
-WebrtcConnectionToClient::~WebrtcConnectionToClient() {}
+WebrtcConnectionToClient::~WebrtcConnectionToClient() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
 
 void WebrtcConnectionToClient::SetEventHandler(
     ConnectionToClient::EventHandler* event_handler) {