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

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

Index: mojo/public/cpp/bindings/lib/router.h
diff --git a/mojo/public/cpp/bindings/lib/router.h b/mojo/public/cpp/bindings/lib/router.h
index d51dceda878a278a09462b2e2ede7b74269133af..6cee1d67f9d70c22f5bdb66755724c32c8a0f587 100644
--- a/mojo/public/cpp/bindings/lib/router.h
+++ b/mojo/public/cpp/bindings/lib/router.h
@@ -132,6 +132,10 @@ class Router : public MessageReceiverWithResponder {
     return &control_message_proxy_;
   }
 
+  bool SimulateReceivingMessageForTesting(Message* message) {
+    return filters_.Accept(message);
+  }
+
  private:
   // Maps from the id of a response to the MessageReceiver that handles the
   // response.