[remoting android] Implement HostService.

remoting/android/host/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!--
   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.
 -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.chromium.chromoting.host">
     <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="23"/>
     <uses-permission android:name="android.permission.INTERNET"/>
     <application android:label="CRD Host"
         android:name="org.chromium.chromoting.host.RemotingApplication"
         android:theme="@style/Theme.AppCompat.Light.NoActionBar"
         android:allowBackup="false">
         <meta-data
                 android:name="com.google.android.gms.version"
                 android:value="@integer/google_play_services_version"/>
         <activity android:name="org.chromium.chromoting.host.MainActivity"
             android:launchMode="singleTask">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+        <service android:name="org.chromium.chromoting.host.HostService"/>
     </application>
 </manifest>