android_webview: support building a stub WebView.

android_webview/apk/java/AndroidManifest.xml

Index: android_webview/apk/java/AndroidManifest.xml
diff --git a/android_webview/apk/java/AndroidManifest.xml b/android_webview/apk/java/AndroidManifest.xml
index 0e0ac96a6ba93d13884dd57cc41a7eba2e0e463e..79ef31b024c6cf7379c69e9f039b5d5034807154 100644
--- a/android_webview/apk/java/AndroidManifest.xml
+++ b/android_webview/apk/java/AndroidManifest.xml
@@ -45,7 +45,11 @@
                      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"