[mojo] Add GenericInterface_ to interface class variants

mojo/public/cpp/bindings/associated_group.h

Index: mojo/public/cpp/bindings/associated_group.h
diff --git a/mojo/public/cpp/bindings/associated_group.h b/mojo/public/cpp/bindings/associated_group.h
index b6934e09eb48728d380c728f15998b5c44b15d33..e46a73872a6750387b03b9ed6b9323a569032106 100644
--- a/mojo/public/cpp/bindings/associated_group.h
+++ b/mojo/public/cpp/bindings/associated_group.h
@@ -44,16 +44,17 @@ class AssociatedGroup {
   // no need to wait until |request| is bound to an implementation at the remote
   // side.
   template <typename T>
-  void CreateAssociatedInterface(AssociatedInterfaceConfig config,
-                                 AssociatedInterfacePtrInfo<T>* ptr_info,
-                                 AssociatedInterfaceRequest<T>* request) {
+  void CreateAssociatedInterface(
+      AssociatedInterfaceConfig config,
+      AssociatedInterfacePtrInfo<T>* ptr_info,

[yzshen1, 2015/12/14 23:58:26]

ptr_info should use the same type as the request, right?

InterfacePtrInfo <-> InterfacePtr is exactly the same relationship as
InterfaceRequest <-> Binding. So we probably don't want |ptr_info| to use a
"variant" type.

Therefore, it seems correct to leave this method untouched. WDYT?

+      AssociatedInterfaceRequest<typename T::GenericInterface>* request) {
     internal::ScopedInterfaceEndpointHandle local;
     internal::ScopedInterfaceEndpointHandle remote;
     CreateEndpointHandlePair(&local, &remote);
 
     if (!local.is_valid() || !remote.is_valid()) {
       *ptr_info = AssociatedInterfacePtrInfo<T>();
-      *request = AssociatedInterfaceRequest<T>();
+      *request = AssociatedInterfaceRequest<typename T::GenericInterface>();
       return;
     }