Add missing permission for webview tests

android_webview/test/shell/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 
 <!-- Copyright 2013 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.android_webview.shell">
   <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="23" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
   <uses-permission android:name="android.permission.INTERNET"/>
+  <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
   <uses-permission android:name="android.permission.WAKE_LOCK"/>
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
   <uses-permission android:name="android.permission.RECORD_AUDIO" />
   <uses-permission android:name="android.permission.RECORD_VIDEO" />
   <uses-permission android:name="android.permission.CAMERA" />
 
   <!-- Kerberos authentication -->
   <uses-permission android:name="android.permission.GET_ACCOUNTS" />
   <uses-permission android:name="android.permission.USE_CREDENTIALS" />
 
@@ skipping 25 matching lines @@
              android:exported="false" />
     <meta-data android:name="org.chromium.content.browser.NUM_PRIVILEGED_SERVICES"
                android:value="0"/>
     <!-- See AwSecondBrowserProcessTest -->
     <service android:name="org.chromium.android_webview.test.SecondBrowserProcess"
              android:process=":second_browser_process"
              android:isolatedProcess="false"
              android:exported="false" />
   </application>
 </manifest>