CPP bindings: DCHECK when a Callback is destructed without being invoked

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

Index: mojo/public/cpp/bindings/lib/router.cc
diff --git a/mojo/public/cpp/bindings/lib/router.cc b/mojo/public/cpp/bindings/lib/router.cc
index da1e7e122024496d9e1f0433497d3712af591573..e64f1fa0a1224100b615ad83df28d0b21b755a9c 100644
--- a/mojo/public/cpp/bindings/lib/router.cc
+++ b/mojo/public/cpp/bindings/lib/router.cc
@@ -11,7 +11,7 @@ namespace internal {
 
 // ----------------------------------------------------------------------------
 
-class ResponderThunk : public MessageReceiver {
+class ResponderThunk : public MessageReceiverWithStatus {
  public:
   explicit ResponderThunk(const SharedData<Router*>& router)
       : router_(router), accept_was_invoked_(false) {}
@@ -44,6 +44,12 @@ class ResponderThunk : public MessageReceiver {
     return result;
   }
 
+  // MessageReceiverWithStatus implementation:
+  bool IsValid() override {
+    Router* router = router_.value();
+    return router && !router->encountered_error() && router->is_valid();
+  }
+
  private:
   SharedData<Router*> router_;
   bool accept_was_invoked_;
@@ -118,7 +124,7 @@ void Router::EnableTestingMode() {
 bool Router::HandleIncomingMessage(Message* message) {
   if (message->has_flag(kMessageExpectsResponse)) {
     if (incoming_receiver_) {
-      MessageReceiver* responder = new ResponderThunk(weak_self_);
+      MessageReceiverWithStatus* responder = new ResponderThunk(weak_self_);
       bool ok = incoming_receiver_->AcceptWithResponder(message, responder);
       if (!ok)
         delete responder;