anchor.diff:        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"
  +  option "with-dartium", "Download and install Dartium -- Chromium with Dart"
   
     resource "content_shell" do
       version "$stableVersion"
  
positive.code:   var hashes = <String, Map>{};
    for (var channel in CHANNELS) {
      hashes[channel] = {};
      for (var file in FILES) {
        var hash = await getHash256(channel, revisions[channel], file);
        hashes[channel][file] = hash;
      }
  
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';
  