anchor.diff:   * A [Source] implementation based of a file in the SDK.
    */
   class SdkSource extends Source {
  -  final spark.DartSdk _sdk;
  +  final sdk.DartSdk _sdk;
     final String fullName;
   
     SdkSource(this._sdk, this.fullName);
  
positive.code: class ChromeDartSdk extends DartSdk {
    final AnalysisContext context;
  
    spark.DartSdk _sdk;
    LibraryMap _libraryMap;
  
    ChromeDartSdk._(this._sdk): context = new AnalysisContextImpl() {
  
negative.code: import 'package:chrome/chrome_app.dart' as chrome;
  import 'package:path/path.dart' as path;
  
  import 'dart/sdk.dart' as sdk;
  
  export 'package:analyzer/src/generated/ast.dart';
  export 'package:analyzer/src/generated/error.dart';
  