Reland "Replace Chrome IPC with Mojo IPC for querying BatteryStatus service"

device/battery/battery_monitor.mojom

Index: device/battery/battery_monitor.mojom
diff --git a/device/battery/battery_monitor.mojom b/device/battery/battery_monitor.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..3648a745e3b29a69606367ed31ed97e9bff60951
--- /dev/null
+++ b/device/battery/battery_monitor.mojom
@@ -0,0 +1,18 @@
+// Copyright 2014 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.
+
+import "device/battery/battery_status.mojom"
+
+module device {
+
+// A BatteryMonitor will periodically call its client's DidChange method.
+[Client=BatteryStatusObserver]
+interface BatteryMonitor {
+};
+
+interface BatteryStatusObserver {
+  DidChange(BatteryStatus status);
+};
+
+}