Support custom message filtering on Mojo binding objects

mojo/public/cpp/bindings/message.h

 // Copyright 2014 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_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 182 matching lines @@
   // |responder| and will delete it after calling |responder->Accept| or upon
   // its own destruction.
   //
   // TODO(yzshen): consider changing |responder| to
   // std::unique_ptr<MessageReceiver>.
   virtual bool AcceptWithResponder(Message* message,
                                    MessageReceiverWithStatus* responder)
       WARN_UNUSED_RESULT = 0;
 };
 
+class PassThroughFilter : public MessageReceiver {
+ public:
+  PassThroughFilter();
+  ~PassThroughFilter() override;
+
+  // MessageReceiver:
+  bool Accept(Message* message) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PassThroughFilter);
+};
+
 namespace internal {
 class SyncMessageResponseSetup;
 }
 
 // An object which should be constructed on the stack immediately before making
 // a sync request for which the caller wishes to perform custom validation of
 // the response value(s). It is illegal to make more than one sync call during
 // the lifetime of the topmost SyncMessageResponseContext, but it is legal to
 // nest contexts to support reentrancy.
 //
@@ skipping 44 matching lines @@
 // Acquires a callback which may be run to report the currently dispatching
 // Message as bad. Note that this is only legal to call from directly within the
 // stack frame of a message dispatch, but the returned callback may be called
 // exactly once any time thereafter to report the message as bad. This may only
 // be called once per message.
 ReportBadMessageCallback GetBadMessageCallback();
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_