Add more generic support for java targets bundling multiple directories

android_webview/java/android_webview_apk.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.
 -->
 <project name="AndroidWebView" default="debug" basedir=".">
   <description>
     Building AndroidWebView.apk
   </description>
@@ skipping 15 matching lines @@
   <path id="native.libs.gdbserver">
     <fileset file="${android.gdbserver}"/>
   </path>
   <property name="native.libs.absolute.dir" location="${out.dir}/libs"/>
   <property name="asset.absolute.dir" location="${out.dir}/assets"/>
   <!-- Set the output directory for the final apk to the ${apks.dir}. -->
   <property-location name="out.final.file"
       location="${apks.dir}/${ant.project.name}-debug.apk"
       check-exists="false"/>
 
+  <path id="javac.srcdirs.additional">
+    <filelist files="${ADDITIONAL_SRC_DIRS}"/>
+    <filelist files="${GENERATED_SRC_DIRS}"/>
+  </path>
+
   <path id="out.dex.jar.input.ref">
     <filelist files="${INPUT_JARS_PATHS}"/>
   </path>
   <echo>resources: ${RESOURCE_DIR} classpath: ${toString:out.dex.jar.input.ref}</echo>
   <target name="-post-compile">
     <!--
       Copy gdbserver to main libs directory if building debug.
       TODO(jrg): for now, Chrome on Android always builds native code
       as Release and java/ant as Debug, which means we always install
       gdbserver.  Resolve this discrepancy, possibly by making this
@@ skipping 13 matching lines @@
   </target>
 
   <!-- Classpath for javac -->
   <path id="javac.custom.classpath">
     <path refid="out.dex.jar.input.ref"/>
   </path>
 
   <import file="../../build/android/ant/sdk-targets.xml"/>
   <import file="${sdk.dir}/tools/ant/build.xml"/>
 </project>