mus: Forward user activity from window server to detector.

ash/mus/user_activity_forwarder.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 ASH_MUS_USER_ACTIVITY_FORWARDER_H_
+#define ASH_MUS_USER_ACTIVITY_FORWARDER_H_
+
+#include "base/macros.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "services/ui/public/interfaces/user_activity_monitor.mojom.h"
+
+namespace service_manager {
+class Connector;
+}
+
+namespace ui {
+class UserActivityDetector;
+}
+
+namespace ash {
+namespace mus {
+
+// Helper class that receives reports of user activity from UserActivityMonitor
+// and forwards them to ui::UserActivityDetector.
+// TODO(derat): Make current ui::UserActivityObserver implementations (i.e.
+// downstream of ui::UserActivityDetector) instead observe UserActivityMonitor
+// directly: http://crbug.com/626899
+class UserActivityForwarder : public ui::mojom::UserActivityObserver {

[James Cook, 2017/01/18 17:01:38]

I wonder if this class could live under //ui. While //services/ui has DEPS +ui,
the public interfaces should not actually depend on much of //ui. I wonder if it
would work to make the //ui/base/user_activity code into its own module (not
part of //ui/base), perhaps under //ui/chromeos/user_activity. This class could
still exist, but be optionally constructed by the ash process and the chrome
browser process when running in mash.

This class could also continue to live here, and chrome browser could depend on
this directory, but that would be somewhat confusing, as we're trying to
eliminate chrome -> ash dependencies in general.

WDYT?

[Daniel Erat, 2017/01/18 18:54:20]

are you proposing something like the following?

- leave services/ui/DEPS alone
- add -ui/chromeos to a new services/ui/public/DEPS file
- move this class to ui/chromeos/user_activity
- add +services/ui/public to ui/chromeos/user_activity/DEPS

(perhaps both of those .../public paths should be .../public/interfaces.)

that might work, but it makes the relationship between //services/ui and //ui
feel really tricky to me.

[James Cook, 2017/01/18 20:17:32]

If you look under //ui you'll see several cases where DEPS allows
+services/service_manager and +services/ui/public

I was thinking:
- change services/ui/DEPS to remove +ui and add +ui/foo for all foo it actually
uses.
- add +services/ui/public to ui/chromeos/user_activity

What you're doing now is OK with me for ash, but how are you going to deal with
the user activity observers in chrome browser?

+ public:
+  UserActivityForwarder(service_manager::Connector* connector,
+                        ui::UserActivityDetector* detector);
+  ~UserActivityForwarder() override;
+
+ private:
+  // ui::mojom::UserActivityObserver:
+  void OnUserActivity() override;
+
+  ui::mojom::UserActivityMonitorPtr user_activity_monitor_;
+  mojo::Binding<ui::mojom::UserActivityObserver>
+      user_activity_observer_binding_;
+
+  ui::UserActivityDetector* user_activity_detector_;  // Not owned.
+
+  DISALLOW_COPY_AND_ASSIGN(UserActivityForwarder);
+};
+
+}  // namespace mus
+}  // namespace ash
+
+#endif  // ASH_MUS_USER_ACTIVITY_FORWARDER_H_