Support custom message filtering on Mojo binding objects

mojo/public/cpp/bindings/message.h

Index: mojo/public/cpp/bindings/message.h
diff --git a/mojo/public/cpp/bindings/message.h b/mojo/public/cpp/bindings/message.h
index df05faeee1273c34b793ad8ce0095e20b8360481..9cce92c8e0419cfa2b7f7c04b7d2e485e1af654b 100644
--- a/mojo/public/cpp/bindings/message.h
+++ b/mojo/public/cpp/bindings/message.h
@@ -200,6 +200,18 @@ class MessageReceiverWithResponderStatus : public MessageReceiver {
       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;
 }