Allow Mojo structs as map keys

mojo/public/cpp/bindings/map_traits_wtf_hash_map.h

 // Copyright 2016 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_MAP_TRAITS_WTF_HASH_MAP_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_MAP_TRAITS_WTF_HASH_MAP_H_
 
 #include "base/logging.h"
 #include "mojo/public/cpp/bindings/map_traits.h"
 #include "third_party/WebKit/Source/wtf/HashMap.h"
@@ skipping 28 matching lines @@
 
   static void AdvanceIterator(ConstIterator& iterator) { ++iterator; }
   static void AdvanceIterator(Iterator& iterator) { ++iterator; }
 
   static const K& GetKey(Iterator& iterator) { return iterator->key; }
   static const K& GetKey(ConstIterator& iterator) { return iterator->key; }
 
   static V& GetValue(Iterator& iterator) { return iterator->value; }
   static const V& GetValue(ConstIterator& iterator) { return iterator->value; }
 
-  static bool Insert(WTF::HashMap<K, V>& input, const K& key, V&& value) {
+  template <typename IK, typename IV>
+  static bool Insert(WTF::HashMap<K, V>& input, IK&& key, IV&& value) {
     if (!WTF::HashMap<K, V>::isValidKey(key)) {
-      LOG(ERROR) << "The key value is disallowed by WTF::HashMap: " << key;
+      LOG(ERROR) << "The key value is disallowed by WTF::HashMap";
       return false;
     }
-    input.add(key, std::forward<V>(value));
-    return true;
-  }
-  static bool Insert(WTF::HashMap<K, V>& input, const K& key, const V& value) {
-    if (!WTF::HashMap<K, V>::isValidKey(key)) {
-      LOG(ERROR) << "The key value is disallowed by WTF::HashMap: " << key;
-      return false;
-    }
-    input.add(key, value);
+    input.add(std::forward<IK>(key), std::forward<IV>(value));
     return true;
   }
 
   static void SetToEmpty(WTF::HashMap<K, V>* output) { output->clear(); }
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MAP_TRAITS_WTF_HASH_MAP_H_