anchor.diff:    CompilerOptions options = getOptions();
     IncrementalCompiler compiler =
         new IncrementalKernelGenerator(options, dart2jsUrl);
  -  var y = await compiler.computeDelta();
  -  await writeProgramToFile(y, normalDill);
  +  var program = await compiler.computeDelta();
  +  List<int> data = serializeProgram(program);
  +  fs.entityForUri(normalDill).writeAsBytesSync(data);
     return compiler.bootstrapSuccess;
   }
   
  
positive.code:   var options = new CompilerOptions()
      ..sdkRoot = sdkRoot
      ..librariesSpecificationUri = Uri.base.resolve("sdk/lib/libraries.json")
      ..strongMode = false;
    return options;
  }
  
  
negative.code:   compiler.invalidate(invalidateUri);
    var bootstrappedProgram = await compiler.computeDelta();
    bool result = compiler.bootstrapSuccess;
    List<int> data = serializeProgram(bootstrappedProgram);
    fs.entityForUri(bootstrappedDill).writeAsBytesSync(data);
    compiler.invalidate(invalidateUri);
  
    var partialProgram = await compiler.computeDelta();
  