anchor.diff:    var hashes = <String, Map>{};
     for (var channel in CHANNELS) {
       hashes[channel] = {};
  -    for (var file in FILES) {
  +    for (var file in FILES[channel]) {
         var hash = await getHash256(channel, revisions[channel], file);
         hashes[channel][file] = hash;
       }
  
positive.code:       url "$urlBase/dev/release/${revisions['dev']}/$ia32File"
        sha256 "${hashes['dev'][ia32File]}"
      end
  
      resource "content_shell" do
        version "$devVersion"
        url "$urlBase/dev/release/${revisions['dev']}/$contentShellFile"
        sha256 "${hashes['dev'][contentShellFile]}"
      end
  
      resource "dartium" do
        version "$devVersion"
        url "$urlBase/dev/release/${revisions['dev']}/$dartiumFile"
        sha256 "${hashes['dev'][dartiumFile]}"
      end
    end
  
    option "with-content-shell", "Download and install content_shell -- headless Dartium for testing"
    option "with-dartium", "Download and install Dartium -- Chromium with Dar"
  
    resource "content_shell" do
      version "$stableVersion"
  
negative.code: 
  const CHANNELS = const ['dev', 'stable'];
  
  const FILES = const {
    'dev': const [x64File, ia32File],
    'stable': const [x64File, ia32File, dartiumFile, contentShellFile]
  };
  
  const urlBase = 'https://storage.googleapis.com/dart-archive/channels';
  const x64File = 'sdk/dartsdk-macos-x64-release.zip';
  