Reland of Use std::tie() for operator< in components/

components/mus/ws/ids.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 COMPONENTS_MUS_WS_IDS_H_
 #define COMPONENTS_MUS_WS_IDS_H_
 
+#include <tuple>
+
 #include "components/mus/common/types.h"
 #include "components/mus/common/util.h"
 
 namespace mus {
 
 namespace ws {
 
 // Connection id is used to indicate no connection. That is, no WindowTreeImpl
 // ever gets this id.
 const ConnectionSpecificId kInvalidConnectionId = 0;
 
 // Adds a bit of type safety to window ids.
 struct WindowId {
   WindowId(ConnectionSpecificId connection_id, ConnectionSpecificId window_id)
       : connection_id(connection_id), window_id(window_id) {}
   WindowId() : connection_id(0), window_id(0) {}
 
   bool operator==(const WindowId& other) const {
     return other.connection_id == connection_id && other.window_id == window_id;
   }
 
   bool operator!=(const WindowId& other) const { return !(*this == other); }
 
   bool operator<(const WindowId& other) const {
-    if (connection_id == other.connection_id)
-      return window_id < other.window_id;
-
-    return connection_id < other.connection_id;
+    return std::tie(connection_id, window_id) <
+           std::tie(other.connection_id, other.window_id);
   }
 
   ConnectionSpecificId connection_id;
   ConnectionSpecificId window_id;
 };
 
 inline WindowId WindowIdFromTransportId(Id id) {
   return WindowId(HiWord(id), LoWord(id));
 }
 
@@ skipping 10 matching lines @@
 // Returns a root window id with a given index offset.
 inline WindowId RootWindowId(uint16_t index) {
   return WindowId(kInvalidConnectionId, 2 + index);
 }
 
 }  // namespace ws
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_IDS_H_