mash: Replace int ShelfIDs with AppLaunchID strings.

ash/public/cpp/app_launch_id.h

 // Copyright 2017 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 ASH_PUBLIC_CPP_APP_LAUNCH_ID_H_
 #define ASH_PUBLIC_CPP_APP_LAUNCH_ID_H_
 
 #include <string>
 
 #include "ash/public/cpp/ash_public_export.h"
 
 namespace ash {
 
 // A unique shelf item id composed of an |app_id| and a |launch_id|.
 // |app_id| is the non-empty application id associated with a set of windows.
 // |launch_id| is passed on app launch, to support multiple shelf items per app.
 // As an example, a remote desktop client may want each remote application to
 // have its own icon.
 class ASH_PUBLIC_EXPORT AppLaunchId {
  public:
   AppLaunchId(const std::string& app_id, const std::string& launch_id);
   // Creates an AppLaunchId with an empty |launch_id|.
   explicit AppLaunchId(const std::string& app_id);
   // Empty constructor for pre-allocating.
   AppLaunchId();
   ~AppLaunchId();
 
-  AppLaunchId(const AppLaunchId& app_launch_id) = default;
-  AppLaunchId(AppLaunchId&& app_launch_id) = default;
-  AppLaunchId& operator=(const AppLaunchId& other) = default;
+  AppLaunchId(const AppLaunchId& other);
+  AppLaunchId(AppLaunchId&& other);
+  AppLaunchId& operator=(const AppLaunchId& other);
+  bool operator==(const AppLaunchId& other) const;
+  bool operator!=(const AppLaunchId& other) const;
+  bool operator<(const AppLaunchId& other) const;
 
-  const std::string& app_id() const { return app_id_; }
-  const std::string& launch_id() const { return launch_id_; }
+  // Returns true if both the application id and launch id are empty.
+  // This is often used to determine if the id is invalid.
+  bool IsNull() const;
 
- private:
   // The application id associated with a set of windows.
-  std::string app_id_;
+  std::string app_id;
   // An id passed on app launch, to support multiple shelf items per app.
-  std::string launch_id_;
+  std::string launch_id;
 };
 
 }  // namespace ash
 
 #endif  // ASH_PUBLIC_CPP_APP_LAUNCH_ID_H_