Introduce ash mojo interface for lock screen action handlers

ash/tray_action/tray_action.cc

+// 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.
+
+#include "ash/tray_action/tray_action.h"
+
+#include <utility>
+
+#include "ash/tray_action/tray_action_observer.h"
+#include "base/logging.h"
+
+namespace ash {
+
+TrayAction::TrayAction() = default;
+
+TrayAction::~TrayAction() = default;
+
+void TrayAction::AddObserver(TrayActionObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void TrayAction::RemoveObserver(TrayActionObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void TrayAction::BindRequest(mojom::TrayActionRequest request) {
+  bindings_.AddBinding(this, std::move(request));
+}
+
+mojom::TrayActionState TrayAction::GetLockScreenNoteState() {
+  if (!tray_action_client_)
+    return mojom::TrayActionState::kNotSupported;
+  return lock_screen_note_state_;
+}
+
+void TrayAction::SetClient(mojom::TrayActionClientPtr tray_action_client) {
+  mojom::TrayActionState old_lock_screen_note_state = GetLockScreenNoteState();
+
+  tray_action_client_ = std::move(tray_action_client);
+
+  // Setting action handler value can change effective state - notify observers
+  // if that was the case.
+  if (GetLockScreenNoteState() != old_lock_screen_note_state)

[xiyuan, 2017/05/04 21:19:16]

Do we need to worry about SetClient to nullptr case? If we do, we probably
should handle connection lost and having an Initialize(client, state_in_client)
to set client as well as setting state in the client.

[tbarzic, 2017/05/04 23:27:18]

Yeah good point, I planned to do this, but it slipped my mind :/

+    NotifyLockScreenNoteStateChanged();
+}
+
+void TrayAction::UpdateLockScreenNoteState(mojom::TrayActionState state) {
+  if (state == lock_screen_note_state_)
+    return;
+
+  lock_screen_note_state_ = state;
+
+  if (tray_action_client_)

[xiyuan, 2017/05/04 21:19:16]

Why the notification does not need to fire without an |tray_action_client_| ? I
would think whether there is an |tray_action_client_| is irrelevant on the state
change notification.

[tbarzic, 2017/05/04 23:27:18]

If client us not set, the effective action state has not changed - it's not
supported (as ash cannot handle the action itself).

+    NotifyLockScreenNoteStateChanged();
+}
+
+void TrayAction::RequestNewLockScreenNote() {
+  if (!tray_action_client_)
+    return;
+
+  tray_action_client_->RequestNewLockScreenNote();
+}
+
+void TrayAction::NotifyLockScreenNoteStateChanged() {
+  for (auto& observer : observers_)
+    observer.OnLockScreenNoteStateChanged(GetLockScreenNoteState());
+}
+
+}  // namespace ash