Mojo C++ bindings: more consistent Clone() and Equals().

mojo/public/cpp/bindings/lib/template_util.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_TEMPLATE_UTIL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_TEMPLATE_UTIL_H_
 
+#include <type_traits>
+
 namespace mojo {
 namespace internal {
 
 template <class T, T v>
 struct IntegralConstant {
   static const T value = v;
 };
 
 template <class T, T v>
 const T IntegralConstant<T, v>::value;
@@ skipping 93 matching lines @@
 template <bool B, typename T, typename F>
 struct Conditional {
   typedef T type;
 };
 
 template <typename T, typename F>
 struct Conditional<false, T, F> {
   typedef F type;
 };
 
+template <typename T>
+struct HasCloneMethod {
+  template <typename U>
+  static char Test(decltype(&U::Clone));
+  template <typename U>
+  static int Test(...);
+  static const bool value = sizeof(Test<T>(0)) == sizeof(char);
+
+ private:
+  EnsureTypeIsComplete<T> check_t_;
+};
+
+template <typename T,
+          typename std::enable_if<HasCloneMethod<T>::value>::type* = nullptr>
+T Clone(const T& input) {
+  return input.Clone();
+};
+
+template <typename T,
+          typename std::enable_if<!HasCloneMethod<T>::value>::type* = nullptr>
+T Clone(const T& input) {
+  return input;
+}
+
+template <typename T>
+struct HasEqualsMethod {
+  template <typename U>
+  static char Test(decltype(&U::Equals));
+  template <typename U>
+  static int Test(...);
+  static const bool value = sizeof(Test<T>(0)) == sizeof(char);
+
+ private:
+  EnsureTypeIsComplete<T> check_t_;
+};
+
+template <typename T,
+          typename std::enable_if<HasEqualsMethod<T>::value>::type* = nullptr>
+bool Equals(const T& a, const T& b) {
+  return a.Equals(b);
+};
+
+template <typename T,
+          typename std::enable_if<!HasEqualsMethod<T>::value>::type* = nullptr>
+bool Equals(const T& a, const T& b) {
+  return a == b;
+}
+
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_TEMPLATE_UTIL_H_