Remove use of std::function from Mojo internals

mojo/edk/system/ports/node.cc

Index: mojo/edk/system/ports/node.cc
diff --git a/mojo/edk/system/ports/node.cc b/mojo/edk/system/ports/node.cc
index 93bb7c38b727ce0a6fd56d967b561b3409f052d8..186e8aaad95795f6f608555a0d7c16d17a73db40 100644
--- a/mojo/edk/system/ports/node.cc
+++ b/mojo/edk/system/ports/node.cc
@@ -263,16 +263,12 @@ int Node::GetStatus(const PortRef& port_ref, PortStatus* port_status) {
   return OK;
 }
 
-int Node::GetMessage(const PortRef& port_ref, ScopedMessage* message) {
-  return GetMessageIf(port_ref, nullptr, message);
-}
-
-int Node::GetMessageIf(const PortRef& port_ref,
-                       std::function<bool(const Message&)> selector,
-                       ScopedMessage* message) {
+int Node::GetMessage(const PortRef& port_ref,
+                     ScopedMessage* message,
+                     MessageFilter* filter) {
   *message = nullptr;
 
-  DVLOG(4) << "GetMessageIf for " << port_ref.name() << "@" << name_;
+  DVLOG(4) << "GetMessage for " << port_ref.name() << "@" << name_;
 
   Port* port = port_ref.port();
   {
@@ -288,7 +284,7 @@ int Node::GetMessageIf(const PortRef& port_ref,
     if (!CanAcceptMoreMessages(port))
       return ERROR_PORT_PEER_CLOSED;
 
-    port->message_queue.GetNextMessageIf(std::move(selector), message);
+    port->message_queue.GetNextMessage(message, filter);
   }
 
   // Allow referenced ports to trigger PortStatusChanged calls.
@@ -994,7 +990,7 @@ int Node::AcceptPort(const PortName& port_name,
            << port->last_sequence_num_to_receive << "]";
 
   // A newly accepted port is not signalable until the message referencing the
-  // new port finds its way to the consumer (see GetMessageIf).
+  // new port finds its way to the consumer (see GetMessage).
   port->message_queue.set_signalable(false);
 
   int rv = AddPortWithName(port_name, port);
@@ -1176,7 +1172,7 @@ int Node::ForwardMessages_Locked(const LockedPort& port,
 
   for (;;) {
     ScopedMessage message;
-    port->message_queue.GetNextMessageIf(nullptr, &message);
+    port->message_queue.GetNextMessage(&message, nullptr);
     if (!message)
       break;