Update targetSdkVersion to 20.

content/shell/android/shell_apk/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 
 <!-- Copyright (c) 2012 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.content_shell_apk">
@@ skipping 116 matching lines @@
                  android:exported="false" />
         <service android:name="org.chromium.content.app.SandboxedProcessService19"
                  android:process=":sandboxed_process19"
                  android:permission="org.chromium.content_shell.permission.SANDBOX"
                  android:isolatedProcess="true"
                  android:exported="false" />
         <meta-data android:name="org.chromium.content.browser.SMART_CLIP_PROVIDER"
                    android:value="org.chromium.content.browser.SmartClipProvider" />
     </application>
 
-    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19" />
+    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="20" />
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
     <uses-permission android:name="android.permission.CAMERA"/>
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
     <uses-permission android:name="android.permission.RECORD_AUDIO"/>
     <uses-permission android:name="android.permission.VIBRATE"/>
     <uses-permission android:name="android.permission.WAKE_LOCK"/>
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
 </manifest>