Introduce ash mojo interface for lock screen action handlers

chrome/browser/ui/ash/tray_action_handler_client.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_UI_ASH_TRAY_ACTION_HANDLER_CLIENT_H_
+#define CHROME_BROWSER_UI_ASH_TRAY_ACTION_HANDLER_CLIENT_H_
+
+#include "ash/public/interfaces/tray_action_handler.mojom.h"
+#include "base/scoped_observer.h"
+#include "chrome/browser/chromeos/lock_screen_apps/state_observer.h"
+#include "mojo/public/cpp/bindings/binding.h"
+
+namespace lock_screen_apps {
+class StateController;
+}
+
+// Chrome implementation of ash action handler interface.
+// Delegates action requests from ash to lock_sreen_apps::StateController and
+// lock screen apps state changes from lock_screen_apps::StateController to ash.
+class TrayActionHandlerClient : public ash::mojom::TrayActionHandlerClient,

[James Cook, 2017/05/03 23:31:52]

High-level comment: Do you need this class at all? The
lock_screen_apps::StateController could be the TrayActionClient, and it could
grab the mojo interface pointer and call it when necessary. That would eliminate
a layer of observers and calls back and forth.

If you do decide to keep this class, it needs test coverage.

[tbarzic, 2017/05/04 20:58:31]

OK, done. I though it might be useful to separate concepts to make the interface
easier to reuse for other actions, but I guess that can be done later, if
needed.

+                                public lock_screen_apps::StateObserver {
+ public:
+  explicit TrayActionHandlerClient(
+      lock_screen_apps::StateController* state_controller);
+  ~TrayActionHandlerClient() override;
+
+  // Initializes the handlers mojo bindings.
+  void Init();
+
+  // ash::mojom::ActionHandler impl:

[James Cook, 2017/05/03 23:31:51]

nit: no "impl:", just ":" or "overrides:" or something else more common in
chrome

[tbarzic, 2017/05/04 20:58:31]

Done.

+  void RequestHandleAction(ash::mojom::TrayActionHandlerAction action) override;
+
+  // lock_screen_apps::StateObserver impl:
+  void OnLockScreenAppsStateChanged(
+      lock_screen_apps::Action action,
+      lock_screen_apps::ActionState state) override;
+
+ private:
+  lock_screen_apps::StateController* lock_screen_apps_state_controller_;
+  ScopedObserver<lock_screen_apps::StateController,
+                 lock_screen_apps::StateObserver>
+      observer_;
+
+  mojo::Binding<ash::mojom::TrayActionHandlerClient> binding_;
+  ash::mojom::TrayActionHandlerControllerPtr tray_action_handler_controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayActionHandlerClient);
+};
+
+#endif  // CHROME_BROWSER_UI_ASH_TRAY_ACTION_HANDLER_CLIENT_H_