anchor.diff:  class ChromeDartSdk extends DartSdk {
     final AnalysisContext context;
   
  -  spark.DartSdk _sdk;
  +  sdk.DartSdk _sdk;
     LibraryMap _libraryMap;
   
     ChromeDartSdk._(this._sdk): context = new AnalysisContextImpl() {
  
positive.code: 
    _sdkCompleter = new Completer();
  
    spark.DartSdk.createSdk().then((spark.DartSdk sdk) {
      ChromeDartSdk chromeSdk = new ChromeDartSdk._(sdk);
      chromeSdk._parseLibrariesFile();
      _sdkCompleter.complete(chromeSdk);
  
negative.code:  * A [Source] implementation based of a file in the SDK.
   */
  class SdkSource extends Source {
    final sdk.DartSdk _sdk;
    final String fullName;
  
    SdkSource(this._sdk, this.fullName);
  