nfc: Various fixes to the NFC D-Bus client in chromeos/dbus.

chromeos/dbus/nfc_client_helpers.h

Index: chromeos/dbus/nfc_client_helpers.h
diff --git a/chromeos/dbus/nfc_client_helpers.h b/chromeos/dbus/nfc_client_helpers.h
index dedd4a4ce5a93711e231c007b7849f82288706b3..e2e8b06bb9b7faf3fff539df4282e21f31837da5 100644
--- a/chromeos/dbus/nfc_client_helpers.h
+++ b/chromeos/dbus/nfc_client_helpers.h
@@ -11,6 +11,7 @@
 
 #include "base/basictypes.h"
 #include "base/callback.h"
+#include "base/values.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/nfc_property_set.h"
 #include "dbus/bus.h"
@@ -44,6 +45,12 @@ CHROMEOS_EXPORT void OnSuccess(const base::Closure& callback,
 CHROMEOS_EXPORT void OnError(const ErrorCallback& error_callback,
                              dbus::ErrorResponse* response);
 
+// Appends any value (basic types and nested types) represented by |value| to
+// the writer |writer| as a variant type.
+// TODO(armansito): Consider moving this to dbus/values_util.h"
+CHROMEOS_EXPORT void AppendValueDataAsVariant(dbus::MessageWriter* writer,
+                                              const base::Value& value);
+
 // DBusObjectMap is a simple data structure that facilitates keeping track of
 // D-Bus object proxies and properties. It maintains a mapping from object
 // paths to object proxy - property structure pairs.