Add AppLauncherId wrapper for items shown in shelf

chrome/browser/ui/ash/chrome_launcher_prefs.h

Index: chrome/browser/ui/ash/chrome_launcher_prefs.h
diff --git a/chrome/browser/ui/ash/chrome_launcher_prefs.h b/chrome/browser/ui/ash/chrome_launcher_prefs.h
index 9f1f5e18cf96332f30f2316e07dbd888cb60f4eb..7fb872e3af4da078089f511364c8be2ad11af624 100644
--- a/chrome/browser/ui/ash/chrome_launcher_prefs.h
+++ b/chrome/browser/ui/ash/chrome_launcher_prefs.h
@@ -51,10 +51,37 @@ extern const char kShelfAlignmentBottom[];
 extern const char kShelfAlignmentLeft[];
 extern const char kShelfAlignmentRight[];
 
+// A unique chrome launcher id used to identify a shelf item.
+class AppLauncherId {
+ public:
+  explicit AppLauncherId(const std::string& app_id);
+  // This constructor is currently unused, but will be used in a follow-up CL.
+  AppLauncherId(const std::string& app_id, const std::string& launch_id);

[James Cook, 2016/10/03 21:14:36]

Document here (or in the class comment above) about the meanings of |app_id|,
|launch_id| and why this class has to exist. (You might be able to reuse the
comments from one of the other launch-id related patches. This is just a good
place to centralize the explanation.)

[Andra Paraschiv, 2016/10/04 11:39:00]

Done.

+  ~AppLauncherId();

[James Cook, 2016/10/03 21:14:36]

What about copy-construction and assignment? I think you should specify those
operators, perhaps with "= default" to be explicit about them.

[Andra Paraschiv, 2016/10/04 11:39:00]

Done.

+
+  const std::string& GetAsString() const { return app_launcher_id_; }
+
+  bool operator==(const AppLauncherId& app_launcher_id) const;
+
+  bool operator!=(const AppLauncherId& app_launcher_id) const;

[James Cook, 2016/10/03 21:14:36]

Do you really need all of these operators? I would guess that you only need
operator== for comparison and operator< for storing in a set.

[Andra Paraschiv, 2016/10/04 11:39:00]

Yes, you are right, we currently need only these comparison operators. Should we
not include the other ones for now?

[James Cook, 2016/10/04 16:08:37]

Yes, only include the ones you need.

[Andra Paraschiv, 2016/10/05 11:21:58]

Done.

+
+  bool operator<(const AppLauncherId& app_launcher_id) const;
+
+  bool operator<=(const AppLauncherId& app_launcher_id) const;
+
+  bool operator>(const AppLauncherId& app_launcher_id) const;
+
+  bool operator>=(const AppLauncherId& app_launcher_id) const;
+
+ private:
+  // A unique chrome launcher id for a shelf item.
+  std::string app_launcher_id_;
+};
+
 void RegisterChromeLauncherUserPrefs(
     user_prefs::PrefRegistrySyncable* registry);
 
-base::DictionaryValue* CreateAppDict(const std::string& app_id);
+base::DictionaryValue* CreateAppDict(const AppLauncherId& app_launcher_id);
 
 // Get or set the shelf auto hide behavior preference for a particular display.
 ShelfAutoHideBehavior GetShelfAutoHideBehaviorPref(PrefService* prefs,
@@ -75,16 +102,16 @@ std::vector<std::string> GetPinnedAppsFromPrefs(
     LauncherControllerHelper* helper);
 
 // Removes information about pin position from sync model for the app.
-void RemovePinPosition(Profile* profile, const std::string& app_id);
+void RemovePinPosition(Profile* profile, const AppLauncherId& app_launcher_id);
 
-// Updates information about pin position in sync model for the app |app_id|.
-// |app_id_before| optionally specifies an app that exists right before the
-// target app. |app_ids_after| optionally specifies sorted by position apps that
-// exist right after the target app.
+// Updates information about pin position in sync model for the app
+// |app_launcher_id|. |app_launcher_id_before| optionally specifies an app that
+// exists right before the target app. |app_launcher_ids_after| optionally
+// specifies sorted by position apps that exist right after the target app.
 void SetPinPosition(Profile* profile,
-                    const std::string& app_id,
-                    const std::string& app_id_before,
-                    const std::vector<std::string>& app_ids_after);
+                    const AppLauncherId& app_launcher_id,
+                    const AppLauncherId& app_launcher_id_before,
+                    const std::vector<AppLauncherId>& app_launcher_ids_after);
 
 // Used to propagate remote preferences to local during the first run.
 class ChromeLauncherPrefsObserver