Introduce lock screen app manager

chrome/browser/chromeos/lock_screen_apps/app_manager.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 CHROME_BROWSER_CHROMEOS_LOCK_SCREEN_APPS_APP_MANAGER_H_
+#define CHROME_BROWSER_CHROMEOS_LOCK_SCREEN_APPS_APP_MANAGER_H_
+
+#include <string>
+
+class Profile;
+
+namespace lock_screen_apps {
+
+// Interface for managing lock screen enabled action handler apps in the lock
+// screen enabled profile. Initially, it will be used primarily to manage lock
+// screen note taking apps.
+class AppManager {
+ public:
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called when note taking availability status changes while the
+    // |AppManager| is active.
+    virtual void OnNoteTakingAvailabilityChanged() = 0;
+  };
+
+  virtual ~AppManager() {}
+
+  // Initializes the manager.
+  // |primary_profile| - the profile which is the source of the lock screen
+  //     action handler app (if one is set). This is the profile whose
+  //     settings are used to determine whether and for which app lock screen
+  //     action is enabled.
+  // |lock_screen_profile| - the profile in which lock screen apps should be
+  //     installed and launched.
+  virtual void Initialize(Profile* primary_profile,
+                          Profile* lock_screen_profile) = 0;
+
+  // Activates the manager - this should ensure that lock screen enabled note
+  // taking app, if available, is loaded and enabled in the lock screen profile.
+  // |observer| - used to notify the user when the note taking app availability
+  //     changes. It's cleared when the |AppManager| is stopped.
+  virtual void Start(Observer* observer) = 0;

[xiyuan, 2017/05/26 22:44:52]

Prefer to use a Callback than using an interface pointer unless we plan to add
more stuff to the interface. The benefit of using a Callback is that we can
decouple the lifetime of an observer with AppManager by using WeakPtr when using
Bind to create the Callback etc.

If we want to use Observer interface, we probably should have a way for an
Observer to remove itself from AppManager (e.g. provide an ObserverDetroyed() in
the interface, or passing WeakPtr instead of raw pointer) or ensure it stays
alive (e.g. scoped_refptr).

Or at least, document the lifetime expectation.

[tbarzic, 2017/05/27 00:48:35]

Done.

+
+  // Stops the manager. After this is called, the app can be unloaded from the
+  // lock screen enabled profile. Subsequent launch requests should not be
+  // allowed.
+  virtual void Stop() = 0;
+
+  // If lock screen note taking app is available, launches the app with lock
+  // screen note taking action.
+  // Returns whether the app launch was attempted.
+  virtual bool LaunchNoteTaking() = 0;
+
+  // Returns whether a lock screen note taking is enabled and ready to launch.
+  virtual bool IsNoteTakingAppAvailable() const = 0;
+
+  // Returns the lock screen enabled lock screen note taking app, if a note
+  // taking app is enabled on lock screen (for primary profile).
+  virtual std::string GetNoteTakingAppId() const = 0;
+};
+
+}  // namespace lock_screen_apps
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOCK_SCREEN_APPS_APP_MANAGER_H_