[Android] Add chrome_java target for building Java code in the chromium layer.

content/shell/android/javatests/content_shell_test_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="ContentShellTest" default="debug" basedir=".">
 
   <description>
     Building ContentShellTest.apk
   </description>
 
-  <property environment="env"/>
-  <property name="sdk.dir" location="${env.ANDROID_SDK_ROOT}"/>
-  <property name="toolchain.dir" location="${env.ANDROID_TOOLCHAIN}"/>
-  <property name="source.dir" location="src"/>
-  <property name="target" value="android-${env.ANDROID_SDK_VERSION}"/>
+  <import file="../../../../build/android/ant/common.xml"/>
+  <import file="../../../../build/android/ant/sdk-targets.xml"/>
   <property name="target.abi" value="${APP_ABI}"/>
   <property name="out.dir" location="${PRODUCT_DIR}/content_shell_test"/>
   <property name="resource.absolute.dir" value="../res"/>
   <property name="gen.absolute.dir" value="${out.dir}/gen"/>
   <path id="native.libs.gdbserver">
     <fileset file="${toolchain.dir}/../../gdbserver"/>
   </path>
   <property name="native.libs.absolute.dir" location="${out.dir}/libs" />
   <property name="asset.absolute.dir" location="${out.dir}/assets" />
 
@@ skipping 36 matching lines @@
          so that proguard can be used to list the tests by annotation. -->
     <jar destfile="${out.dir}/${ant.project.name}-debug.jar">
       <fileset dir="${out.dir}/classes" includes="**/*.class"/>
       <zipfileset
          includes="**/*.class"
          src="${PRODUCT_DIR}/content_shell_test/java/libs/chromium_content_javatests.jar"/>
     </jar>
 
   </target>
 
+  <!-- Classpath for javac -->
+  <path id="javac.custom.classpath">
+    <path refid="out.dex.jar.input.ref"/>
+  </path>
   <import file="${sdk.dir}/tools/ant/build.xml" />
 
 </project>