Mojo C++ bindings: clean up pending callbacks when connection error occurs.

mojo/public/cpp/bindings/lib/interface_endpoint_client.cc

Index: mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
diff --git a/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc b/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
index 1970e9c8e550c485636fc89f739dcf3ceeba484c..5e1978d2086eb445415d517379438ee9e8ceed43 100644
--- a/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
+++ b/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
@@ -266,12 +266,18 @@ void InterfaceEndpointClient::NotifyError() {
   if (encountered_error_)
     return;
   encountered_error_ = true;
+
+  // The callbacks may hold on to resources. There is no need to keep them any
+  // longer.
+  async_responders_.clear();
+
   if (!error_handler_.is_null())
     error_handler_.Run();
 }
 
 bool InterfaceEndpointClient::HandleValidatedMessage(Message* message) {
   DCHECK_EQ(handle_.id(), message->interface_id());
+  DCHECK(!encountered_error_);
 
   if (message->has_flag(Message::kFlagExpectsResponse)) {
     if (!incoming_receiver_)