Mojo: more idiomatic C++ bindings

mojo/public/cpp/bindings/lib/callback_internal.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_LIB_CALLBACK_INTERNAL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_CALLBACK_INTERNAL_H_
 
-#include "mojo/public/cpp/bindings/lib/bindings_internal.h"
+namespace mojo {
+class String;
 
-namespace mojo {
 namespace internal {
 
-template <typename T, bool is_object_type = TypeTraits<T>::kIsObject>
-struct Callback_ParamTraits {};
-
 template <typename T>
-struct Callback_ParamTraits<T, true> {
-  typedef const T& ForwardType;
-  static const bool kIsScopedHandle = false;
+struct Callback_ParamTraits {
+  typedef T ForwardType;
 };
 
-template <typename T>
-struct Callback_ParamTraits<T, false> {
-  typedef T ForwardType;
-  static const bool kIsScopedHandle = false;
+template <>
+struct Callback_ParamTraits<String> {
+  typedef const String& ForwardType;
 };
 
-template <typename H>
-struct Callback_ParamTraits<ScopedHandleBase<H>, true> {
-  typedef ScopedHandleBase<H> ForwardType;
-  static const bool kIsScopedHandle = true;
-};
-
-template<bool B, typename T = void>
-struct EnableIf {};
-
-template<typename T>
-struct EnableIf<true, T> { typedef T type; };
-
-template <typename T>
-typename EnableIf<!Callback_ParamTraits<T>::kIsScopedHandle, T>::type&
-    Callback_Forward(T& t) {
-  return t;
-}
-
-template <typename T>
-typename EnableIf<Callback_ParamTraits<T>::kIsScopedHandle, T>::type
-    Callback_Forward(T& t) {
-  return t.Pass();
-}
-
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_CALLBACK_INTERNAL_H_