Eliminate deferred destruction of AssociatedGroupController

mojo/public/cpp/bindings/lib/multiplex_router.h

Index: mojo/public/cpp/bindings/lib/multiplex_router.h
diff --git a/mojo/public/cpp/bindings/lib/multiplex_router.h b/mojo/public/cpp/bindings/lib/multiplex_router.h
index ccfd1c73dcb403e36ec3b72a481cd5d2100f27d5..6ba9da34c0be3fad0a04e1e4e93704cb304ad2fa 100644
--- a/mojo/public/cpp/bindings/lib/multiplex_router.h
+++ b/mojo/public/cpp/bindings/lib/multiplex_router.h
@@ -47,6 +47,9 @@ namespace internal {
 // Some public methods are only allowed to be called on the creating thread;
 // while the others are safe to call from any threads. Please see the method
 // comments for more details.
+//
+// NOTE: CloseMessagePipe() or PassMessagePipe() MUST be called on |runner|'s
+// thread before this object is destroyed.
 class MultiplexRouter
     : public MessageReceiver,
       public AssociatedGroupController,
@@ -201,6 +204,8 @@ class MultiplexRouter
   // comments of kInterfaceIdNamespaceMask.
   const bool set_interface_id_namespace_bit_;
 
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
   MessageHeaderValidator header_validator_;
   Connector connector_;