Mojoify PoweMonitorMessageBroadcaster IPC from browser to child process

device/power_monitor/public/interfaces/power_monitor.mojom

+// Copyright 2016 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.
+
+module device.mojom;
+
+interface PowerMonitor {
+  // Add client that will be notified on PowerStateChange, Suspend and Resume.
+  AddClient(PowerMonitorClient client);

[Ken Rockot(use gerrit already), 2016/10/25 16:53:13]

nit: I think SetClient is more accurate. AddClient implies you can call it more
than once to bind multiple clients on the same PowerMonitor interface, but that
doesn't appear to be the case.

[ke.he, 2016/10/26 10:01:51]

Done.

+};
+
+interface PowerMonitorClient {
+  // Notification of a change in power status of the computer, such
+  // as from switching between battery and A/C power.
+  PowerStateChange(bool on_battery_power);
+
+  // Notification that the system is suspending.
+  Suspend();
+
+  // Notification that the system is resuming.
+  Resume();
+};