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: import 'package:chrome/chrome_app.dart' as chrome;
  import 'package:path/path.dart' as path;
  
  import 'dart/sdk.dart' as spark;
  
  export 'package:analyzer/src/generated/ast.dart';
  export 'package:analyzer/src/generated/error.dart';
  
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);
  