android_webview: support building a stub WebView.

android_webview/apk/java/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"
     xmlns:tools="http://schemas.android.com/tools"
     package="{{package|default('com.android.webview')}}">
@@ skipping 27 matching lines @@
             <meta-data android:name="com.android.webview.WebViewLibrary"
                     android:value="{{ webview_lib }}" />
             <service android:name="org.chromium.android_webview.crash.CrashReceiverService"
                      android:exported="true"
                      android:process=":crash_receiver_service"/>
             <service android:name="org.chromium.android_webview.crash.MinidumpUploadJobService"
                      android:permission="android.permission.BIND_JOB_SERVICE"
                      android:exported="true"
                      android:process=":crash_receiver_service"/>
         {% endmacro %}
-        {{ common(package|default('com.android.webview'), 'libwebviewchromium.so') }}
+        {{ common(package|default('com.android.webview'), library|default('libwebviewchromium.so')) }}
+        {% if donor_package is defined %}
+          <meta-data android:name="com.android.webview.WebViewDonorPackage"
+                     android:value="{{ donor_package }}" />
+        {% endif %}
         <meta-data android:name="org.chromium.content.browser.NUM_SANDBOXED_SERVICES"
                    android:value="1"/>
         <service android:name="org.chromium.content.app.SandboxedProcessService0"
                  android:process=":sandboxed_process0"
                  android:isolatedProcess="true"
                  android:exported="true"
                  android:externalService="true"
                  tools:ignore="ExportedService" />
         <meta-data android:name="org.chromium.content.browser.NUM_PRIVILEGED_SERVICES"
                    android:value="0"/>
     </application>
 </manifest>