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

mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
index 44d1428d00340edc9472a5e6f2bcba0a5854eca5..8cfe8e5f550b9420190387248e3284d7d590bd19 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
@@ -116,16 +116,21 @@ class {{class_name}}_{{method.name}}_ProxyToResponder
  public:
   virtual ~{{class_name}}_{{method.name}}_ProxyToResponder() {
     delete responder_;
-    // TODO(rudominer) DCHECK if |was_run_| is false and we don't have evidence
-    // that we are in a legitamte shutdown case such as the Connector detected
-    // an error or Close() was invoked.
+    {{class_name}}Stub* stub = associated_stub_.value();
+    if (stub && !stub->connection_error_occurred() && !stub->closed()) {
+      MOJO_DCHECK(was_run_)  << "The callback passed to "
+          "{{class_name}}::{{method.name}}({%- if method.parameters -%}{{pass_params(method.parameters)}}, {% endif -%}callback) "
+          "was never run.";
+    }
   }
 
   {{class_name}}_{{method.name}}_ProxyToResponder(
       uint64_t request_id,
-      mojo::MessageReceiver* responder)
+      mojo::MessageReceiver* responder,
+      const ::mojo::internal::SharedData<{{class_name}}Stub*>& stub)
       : request_id_(request_id),
         responder_(responder),
+        associated_stub_(stub),
         was_run_(false) {
   }
 
@@ -134,6 +139,7 @@ class {{class_name}}_{{method.name}}_ProxyToResponder
  private:
   uint64_t request_id_;
   mutable mojo::MessageReceiver* responder_;
+  ::mojo::internal::SharedData<{{class_name}}Stub*> associated_stub_;
   mutable bool was_run_;
   MOJO_DISALLOW_COPY_AND_ASSIGN({{class_name}}_{{method.name}}_ProxyToResponder);
 };
@@ -156,7 +162,12 @@ void {{class_name}}_{{method.name}}_ProxyToResponder::Run(
 {%- endfor %}
 
 {{class_name}}Stub::{{class_name}}Stub()
-    : sink_(nullptr) {
+    : sink_(nullptr), weak_self_(this), connection_error_occurred_(false), 
+    closed_(false) {
+}
+
+{{class_name}}Stub::~{{interface.name}}Stub() {
+  weak_self_.set_value(nullptr);
 }
 
 {#--- Stub definition #}
@@ -201,7 +212,7 @@ bool {{class_name}}Stub::AcceptWithResponder(
       params->DecodePointersAndHandles(message->mutable_handles());
       {{class_name}}::{{method.name}}Callback::Runnable* runnable =
           new {{class_name}}_{{method.name}}_ProxyToResponder(
-              message->request_id(), responder);
+              message->request_id(), responder, weak_self_);
       {{class_name}}::{{method.name}}Callback callback(runnable);
       {{alloc_params(method|struct_from_method)|indent(4)}}
       // A null |sink_| means no implementation was bound.