Move AcceptWithResponder() out of the MessageReceiver interface.

mojo/public/cpp/bindings/lib/message_filter.cc

Index: mojo/public/cpp/bindings/lib/message_filter.cc
diff --git a/mojo/public/cpp/bindings/lib/message_filter.cc b/mojo/public/cpp/bindings/lib/message_filter.cc
index a5203133160cfed9e25b3292b35a50668b2d91e4..b09f40d8c5efeeecac996cf8868cfaebb39975b5 100644
--- a/mojo/public/cpp/bindings/lib/message_filter.cc
+++ b/mojo/public/cpp/bindings/lib/message_filter.cc
@@ -4,8 +4,6 @@
 
 #include "mojo/public/cpp/bindings/message_filter.h"
 
-#include <assert.h>
-
 namespace mojo {
 
 MessageFilter::MessageFilter(MessageReceiver* sink) : sink_(sink) {
@@ -14,12 +12,6 @@ MessageFilter::MessageFilter(MessageReceiver* sink) : sink_(sink) {
 MessageFilter::~MessageFilter() {
 }
 
-bool MessageFilter::AcceptWithResponder(Message* message,
-                                        MessageReceiver* responder) {
-  assert(false);  // Not reached!
-  return false;
-}
-
 PassThroughFilter::PassThroughFilter(MessageReceiver* sink)
     : MessageFilter(sink) {
 }