[DeviceService] Expose battery monitoring solely via the Device Service

services/device/public/interfaces/BUILD.gn

 # 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("interfaces") {
   sources = [
+    "battery_monitor.mojom",
+    "battery_status.mojom",
     "fingerprint.mojom",
     "power_monitor.mojom",
     "time_zone_monitor.mojom",
     "vibration_manager.mojom",
   ]
 
   public_deps = [
     ":constants",
   ]
 }
 
 mojom("constants") {
   sources = [
     "constants.mojom",
   ]
 }