Upstream Android's PathUtils implementation.

base/android/java/base.xml

 <project name="Base" default="dist" basedir=".">
   <description>
     building base java source code with ant
   </description>
-  <!-- set global properties for this build -->
+  <!-- Set global properties for this build -->
+  <property environment="env"/>
+  <property name="sdk.dir" location="${env.ANDROID_SDK_ROOT}"/>
+  <property name="sdk.version" value="${env.ANDROID_SDK_VERSION}"/>
   <property name="src" location="."/>
   <property name="build" location="build"/>
-  <property name="dist"  location="dist"/>
+  <property name="dist" location="dist"/>
 
   <target name="init">
     <!-- Create the time stamp -->
     <tstamp/>
     <!-- Create the build directory structure used by compile -->
     <mkdir dir="${build}"/>
   </target>
 
   <target name="compile" depends="init"
           description="compile the source " >
     <!-- Compile the java code from ${src} into ${build} -->
-    <javac srcdir="${src}" destdir="${build}"/>
+    <javac srcdir="${src}" destdir="${build}">
+      <classpath>
+        <path location="${sdk.dir}/platforms/android-${sdk.version}/android.jar"/>
+      </classpath>
+    </javac>
   </target>
 
   <target name="dist" depends="compile"
           description="generate the distribution" >
     <!-- Create the distribution directory -->
     <mkdir dir="${dist}/lib"/>
 
     <!-- Put everything in ${build} into the chromium_base.jar file -->
     <jar jarfile="${dist}/lib/chromium_base.jar" basedir="${build}"/>
   </target>
 
   <target name="clean"
           description="clean up" >
     <!-- Delete the ${build} and ${dist} directory trees -->
     <delete dir="${build}"/>
     <delete dir="${dist}"/>
   </target>
 </project>