mus: Forward user activity from window server to detector.

ash/mus/user_activity_forwarder.cc

Index: ash/mus/user_activity_forwarder.cc
diff --git a/ash/mus/user_activity_forwarder.cc b/ash/mus/user_activity_forwarder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2df1368189af15dca9d848b5f828d3ccc709e90a
--- /dev/null
+++ b/ash/mus/user_activity_forwarder.cc
@@ -0,0 +1,43 @@
+// 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/mus/user_activity_forwarder.h"
+
+#include <cmath>
+
+#include "services/service_manager/public/cpp/connector.h"
+#include "services/ui/public/interfaces/constants.mojom.h"
+#include "ui/base/user_activity/user_activity_detector.h"
+
+namespace ash {
+namespace mus {
+
+UserActivityForwarder::UserActivityForwarder(
+    service_manager::Connector* connector,
+    ui::UserActivityDetector* detector)
+    : user_activity_observer_binding_(this), user_activity_detector_(detector) {
+  DCHECK(detector);
+
+  // |connector| is null in some tests.
+  if (connector) {
+    // Round UserActivityDetector's notification interval up to the nearest
+    // second (the granularity exposed by UserActivityMonitor).
+    const uint32_t kNotifyIntervalSec = static_cast<uint32_t>(
+        ceil(ui::UserActivityDetector::kNotifyIntervalMs / 1000.0));
+
+    connector->BindInterface(ui::mojom::kServiceName, &user_activity_monitor_);
+    user_activity_monitor_->AddUserActivityObserver(
+        kNotifyIntervalSec,
+        user_activity_observer_binding_.CreateInterfacePtrAndBind());
+  }
+}
+
+UserActivityForwarder::~UserActivityForwarder() {}
+
+void UserActivityForwarder::OnUserActivity() {
+  user_activity_detector_->HandleExternalUserActivity();
+}

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

If this class sticks around, could it get a trivial unit test? This could be
more-or-less a copy of the one you added, but instead call into OnUserActivity.
This would be testing at the mojo interface, which is something I'm trying to
encourage.

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

hmm. is there any way to exercise the calls to BindInterface and
AddUserActivityObserver from within a unit test, and then tell a stub
implementation of UserActivityMonitor to notify all of its observers? just
checking that OnUserActivity calls HandleExternalUserActivity doesn't feel
likely to catch regressions in the future.

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

I don't know how to exercise the BindInterface bits. I was thinking of ash
SessionController's unit tests. However, in that case the class under test is
processing mojo messages and doing interesting things with them. So I agree
testing at this level probably doesn't add much.

+
+}  // namespace mus
+}  // namespace ash