anchor.diff:  
   const CHANNELS = const ['dev', 'stable'];
   
  -const FILES = const [x64File, ia32File, dartiumFile, contentShellFile];
  +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';
  
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:   var hashes = <String, Map>{};
    for (var channel in CHANNELS) {
      hashes[channel] = {};
      for (var file in FILES[channel]) {
        var hash = await getHash256(channel, revisions[channel], file);
        hashes[channel][file] = hash;
      }
  