Remove use of std::function from Mojo internals

mojo/edk/system/ports/node.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_EDK_SYSTEM_PORTS_NODE_H_
 #define MOJO_EDK_SYSTEM_PORTS_NODE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 26 matching lines @@
   ERROR_PORT_CANNOT_SEND_PEER = -15,
   ERROR_NOT_IMPLEMENTED = -100,
 };
 
 struct PortStatus {
   bool has_messages;
   bool receiving_messages;
   bool peer_closed;
 };
 
+class MessageFilter;
 class NodeDelegate;
 
 class Node {
  public:
   enum class ShutdownPolicy {
     DONT_ALLOW_LOCAL_PORTS,
     ALLOW_LOCAL_PORTS,
   };
 
   // Does not take ownership of the delegate.
@@ skipping 43 matching lines @@
   int ClosePort(const PortRef& port_ref);
 
   // Returns the current status of the port.
   int GetStatus(const PortRef& port_ref, PortStatus* port_status);
 
   // Returns the next available message on the specified port or returns a null
   // message if there are none available. Returns ERROR_PORT_PEER_CLOSED to
   // indicate that this port's peer has closed. In such cases GetMessage may
   // be called until it yields a null message, indicating that no more messages
   // may be read from the port.
-  int GetMessage(const PortRef& port_ref, ScopedMessage* message);
-
-  // Like GetMessage, but the caller may optionally supply a selector function
-  // that decides whether or not to return the message. If |selector| is a
-  // nullptr, then GetMessageIf acts just like GetMessage. The |selector| may
-  // not call any Node methods.
-  int GetMessageIf(const PortRef& port_ref,
-                   std::function<bool(const Message&)> selector,
-                   ScopedMessage* message);
+  //
+  // If |filter| is non-null, the next available message is returned only if it
+  // is matched by the filter. If the provided filter does not match the next
+  // available message, GetMessage() behaves as if there is no message
+  // available. Ownership of |filter| is not taken, and it must outlive the
+  // extent of this call.
+  int GetMessage(const PortRef& port_ref,
+                 ScopedMessage* message,
+                 MessageFilter* filter);
 
   // Sends a message from the specified port to its peer. Note that the message
   // notification may arrive synchronously (via PortStatusChanged() on the
   // delegate) if the peer is local to this Node.
   int SendMessage(const PortRef& port_ref, ScopedMessage message);
 
   // Corresponding to NodeDelegate::ForwardMessage.
   int AcceptMessage(ScopedMessage message);
 
   // Called to merge two ports with each other. If you have two independent
@@ skipping 91 matching lines @@
   std::unordered_map<PortName, scoped_refptr<Port>> ports_;
 
   DISALLOW_COPY_AND_ASSIGN(Node);
 };
 
 }  // namespace ports
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_PORTS_NODE_H_