Introduce ash mojo interface for lock screen action handlers

ash/tray_action/tray_action.h

Index: ash/tray_action/tray_action.h
diff --git a/ash/tray_action/tray_action.h b/ash/tray_action/tray_action.h
new file mode 100644
index 0000000000000000000000000000000000000000..27ea14a15c077376b86edc9d72ed49d86afc0e96
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+++ b/ash/tray_action/tray_action.h
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+// 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_TRAY_ACTION_TRAY_ACTION_H_
+#define ASH_TRAY_ACTION_TRAY_ACTION_H_
+
+#include "ash/ash_export.h"
+#include "ash/public/interfaces/tray_action.mojom.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "mojo/public/cpp/bindings/binding_set.h"
+
+namespace ash {
+
+class TrayActionObserver;
+
+// Controller that ash can use to request a predefined set of actions to be
+// performed by clients.
+// The controller provides an interface to:
+//  * Send a request to the client to handle an action.
+//  * Observe the state of support for an action as reported by the current ash
+//    client.
+// Currently, only single action is supported - creating new note on the lock
+// screen - Chrome handles this action by launching an app (if any) that is
+// registered as a lock screen enabled action handler for the new note action.
+class ASH_EXPORT TrayAction : public NON_EXPORTED_BASE(mojom::TrayAction) {
+ public:
+  TrayAction();
+  ~TrayAction() override;
+
+  void AddObserver(TrayActionObserver* observer);
+  void RemoveObserver(TrayActionObserver* observer);
+
+  void BindRequest(mojom::TrayActionRequest request);
+
+  // Gets last known handler state for the lock screen note action.
+  // It will return kNotAvailable if an action handler has not been set using
+  // |SetClient|.
+  mojom::TrayActionState GetLockScreenNoteState();
+
+  // If the client is set, sends it a request to handle the lock screen note
+  // action.
+  void RequestNewLockScreenNote();
+
+  // mojom::TrayAction:
+  void SetClient(mojom::TrayActionClientPtr action_handler,
+                 mojom::TrayActionState lock_screen_note_state) override;
+  void UpdateLockScreenNoteState(mojom::TrayActionState state) override;
+
+ private:
+  // Notifies the observers that state for the lock screen note action has been
+  // updated.
+  void NotifyLockScreenNoteStateChanged();
+
+  // Last known state for lock screen note action.
+  mojom::TrayActionState lock_screen_note_state_ =
+      mojom::TrayActionState::kNotAvailable;
+
+  base::ObserverList<TrayActionObserver> observers_;
+
+  mojo::BindingSet<mojom::TrayAction> bindings_;
+
+  mojom::TrayActionClientPtr tray_action_client_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayAction);
+};
+
+}  // namespace ash
+
+#endif  // ASH_TRAY_ACTION_TRAY_ACTION_H_