Support custom message filtering on Mojo binding objects

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

Index: mojo/public/cpp/bindings/lib/router.cc
diff --git a/mojo/public/cpp/bindings/lib/router.cc b/mojo/public/cpp/bindings/lib/router.cc
index 7c610eeff571f0d3111d35ebaa3413e6908823c4..5d5db54caa13981a0f96b1f9d0b12826b5963513 100644
--- a/mojo/public/cpp/bindings/lib/router.cc
+++ b/mojo/public/cpp/bindings/lib/router.cc
@@ -133,13 +133,17 @@ Router::Router(ScopedMessagePipeHandle message_pipe,
   filters_.SetSink(&thunk_);
   if (expects_sync_requests)
     connector_.AllowWokenUpBySyncWatchOnSameThread();
-  connector_.set_incoming_receiver(filters_.GetHead());
+  connector_.set_incoming_receiver(&filters_);
   connector_.set_connection_error_handler(
       base::Bind(&Router::OnConnectionError, base::Unretained(this)));
 }
 
 Router::~Router() {}
 
+void Router::AddFilter(std::unique_ptr<MessageReceiver> filter) {
+  filters_.Append(std::move(filter));
+}
+
 bool Router::Accept(Message* message) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!message->has_flag(Message::kFlagExpectsResponse));