Move //webapk to //chrome/android/webapk

chrome/android/webapk/shell_apk/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 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="{{ manifest_package }}"
     android:versionCode="1"
     android:versionName="1.0" >
 
@@ skipping 57 matching lines @@
             android:exported="true"/>
         <service android:name="org.chromium.content.app.PrivilegedProcessService1"
             android:process=":privileged_process1"
             android:exported="true"/>
         <service android:name="org.chromium.content.app.PrivilegedProcessService2"
             android:process=":privileged_process2"
             android:exported="true"/>
     </application>
 
 </manifest>