anchor.diff:  { stdenv, fetchurl, cairo, fontconfig, freetype, gdk_pixbuf, glib
   , glibc, gtk2, libX11, makeWrapper, nspr, nss, pango, unzip, gconf
  -, libXi, libXrender, libXext
  +, libXi, libXrender, libXext, lib
   }:
  -
  -# note: there is a i686 version available as well
  -assert stdenv.system == "x86_64-linux";
  -
  +let
  +  spec = if stdenv.system == "i686-linux" then { system="linux32"; sha256="5d267a8d59f18f1134966e312997b75976f8d816318b5b79b8357a3ac2c022da"; }
  +    else if stdenv.system == "x86_64-linux" then { system="linux64"; sha256="d011749e76305b5591b5500897939b33fac460d705d9815b8c03c53b0e1ecc7c"; }
  +    else if stdenv.system == "x86_64-darwin" then { system="mac64"; sha256="e95fb36ab85264e16c51d58dd9766624eca6b6339569da0460088f4c788c67ad"; }
  +    else abort "missing chromedriver binary for ${stdenv.system}";
  +in
   stdenv.mkDerivation rec {
  -  product = "chromedriver_linux64";
  -  name = "${product}-2.25";
  +  name = "chromedriver-${version}";
     version = "2.25";
   
     src = fetchurl {
  -    url = "http://chromedriver.storage.googleapis.com/${version}/${product}.zip";
  -    sha256 = "0z6c3q73pi83iidq3n85sxhc9yikkf9rf22hnn8manrhfsg784fh";
  +    url = "http://chromedriver.storage.googleapis.com/${version}/chromedriver_${spec.system}.zip";
  +    sha256 = spec.sha256;
     };
   
     buildInputs = [ unzip makeWrapper ];
  
positive.code:   installPhase = ''
      mkdir -p $out/bin
      mv chromedriver $out/bin
      patchelf --set-interpreter ${glibc.out}/lib/ld-linux-x86-64.so.2 $out/bin/chromedriver
      wrapProgram "$out/bin/chromedriver" \
        --prefix LD_LIBRARY_PATH : "${stdenv.lib.makeLibraryPath [ stdenv.cc.cc.lib cairo fontconfig freetype gdk_pixbuf glib gtk2 libX11 nspr nss pango libXrender gconf libXext libXi ]}:\$LD_LIBRARY_PATH"
    '';
  
    meta = with stdenv.lib; {
  
negative.code:     description = "A WebDriver server for running Selenium tests on Chrome";
      license = licenses.bsd3;
      maintainers = [ maintainers.goibhniu ];
      platforms = platforms.linux ++ platforms.darwin;
    };
  }
  