Move AcceptWithResponder() out of the MessageReceiver interface.

mojo/public/cpp/bindings/tests/sample_service_unittest.cc

Index: mojo/public/cpp/bindings/tests/sample_service_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/sample_service_unittest.cc b/mojo/public/cpp/bindings/tests/sample_service_unittest.cc
index a93eb71cfb5be98e44fcf9cdc657eaa01309d418..e06ecd64315ffe09b71502506b1f56687fb418a5 100644
--- a/mojo/public/cpp/bindings/tests/sample_service_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/sample_service_unittest.cc
@@ -287,12 +287,12 @@ class ServiceImpl : public Service {
 
 class ServiceProxyImpl : public ServiceProxy {
  public:
-  explicit ServiceProxyImpl(mojo::MessageReceiver* receiver)
+  explicit ServiceProxyImpl(mojo::MessageReceiverWithResponder* receiver)
       : ServiceProxy(receiver) {
   }
 };
 
-class SimpleMessageReceiver : public mojo::MessageReceiver {
+class SimpleMessageReceiver : public mojo::MessageReceiverWithResponder {
  public:
   virtual bool Accept(mojo::Message* message) MOJO_OVERRIDE {
     // Imagine some IPC happened here.