Mojo C++ bindings: introduce public associated-interface-related types.

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 68d603588724364e9b525747f8916a169f471aa5..b2fb4df3f497160d43890efafafcf3f654e52914 100644
--- a/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
+++ b/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
+#include "mojo/public/cpp/bindings/associated_group.h"
 #include "mojo/public/cpp/bindings/lib/multiplex_router.h"
 
 namespace mojo {
@@ -117,6 +118,12 @@ InterfaceEndpointClient::~InterfaceEndpointClient() {
   handle_.router()->DetachEndpointClient(handle_);
 }
 
+AssociatedGroup* InterfaceEndpointClient::associated_group() {
+  if (!associated_group_)
+    associated_group_ = handle_.router()->CreateAssociatedGroup();
+  return associated_group_.get();
+}
+
 ScopedInterfaceEndpointHandle InterfaceEndpointClient::PassHandle() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!has_pending_responders());