Mojo cpp bindings: add support for validating incoming messages.

mojo/public/cpp/bindings/no_interface.h

Index: mojo/public/cpp/bindings/no_interface.h
diff --git a/mojo/public/cpp/bindings/no_interface.h b/mojo/public/cpp/bindings/no_interface.h
index 02682d4b00445ec35cf3355438a27a7fda1d414d..3d32fe2af06554d8cc28609832e37c2f78159178 100644
--- a/mojo/public/cpp/bindings/no_interface.h
+++ b/mojo/public/cpp/bindings/no_interface.h
@@ -12,6 +12,10 @@
 
 namespace mojo {
 
+// NoValidator is for use in cases when message validation is not needed.
+class NoValidator {
+};
+
 // NoInterface is for use in cases when a non-existent or empty interface is
 // needed (e.g., when the Mojom "Peer" attribute is not present).
 
@@ -22,6 +26,8 @@ class NoInterface {
  public:
   typedef NoInterfaceProxy Proxy_;
   typedef NoInterfaceStub Stub_;
+  typedef NoValidator RequestValidator_;
+  typedef NoValidator ResponseValidator_;
   typedef NoInterface Client_;
   virtual ~NoInterface() {}
   virtual void SetClient(NoInterface* client) {}