anchor.diff:  
   library compiler_configuration;
   
  -import 'dart:io' show Directory, Platform;
  +import 'dart:io' show Platform;
   
   import 'runtime_configuration.dart' show RuntimeConfiguration;
   
  
positive.code:         return new PrecompilerCompilerConfiguration(
              isDebug: isDebug,
              isChecked: isChecked,
              isProduct: isProduct,
              arch: configuration['arch']);
        case 'none':
          return new NoneCompilerConfiguration(
  
negative.code:       CommandBuilder commandBuilder,
        List arguments,
        Map<String, String> environmentOverrides) {
      var exec = "$buildDir/dart_bootstrap";
      var args = new List();
      args.add("--gen-precompiled-snapshot=$tempDir");
      args.addAll(arguments);
  
      return commandBuilder.getCompilationCommand('precompiler', tempDir, !useSdk,
  