Mojo C++ bindings: add more perf tests for Router/MultiplexRouter.

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 0229fcaaac7251412aa32c6ee3d09b1ee61f5f93..84272d3aef4dd66193b54feb0f17d2428e71a679 100644
--- a/mojo/public/cpp/bindings/lib/multiplex_router.h
+++ b/mojo/public/cpp/bindings/lib/multiplex_router.h
@@ -129,6 +129,10 @@ class MultiplexRouter
     return connector_.handle();
   }
 
+  bool SimulateReceivingMessageForTesting(Message* message) {
+    return filters_.Accept(message);
+  }
+
  private:
   class InterfaceEndpoint;
   struct Task;