anchor.diff:  import 'dart:convert';
   import 'dart:core' hide Resource;
   
  -import 'package:analysis_server/uri/resolver_provider.dart';
   import 'package:analyzer/file_system/file_system.dart';
   import 'package:analyzer/source/package_map_resolver.dart';
   import 'package:analyzer/src/generated/source.dart';
   import 'package:analyzer/src/generated/java_io.dart' show JavaFile;
   import 'package:analyzer/src/generated/source_io.dart' show FileBasedSource;
   import 'package:path/path.dart' as pathos;
  +
  +class _SdkExtFileBasedSource extends FileBasedSource {
  +  _SdkExtFileBasedSource(JavaFile file, Uri uri)
  +      : super(file, uri);
  +}
   
   /// Given a packageMap (see [PackageMapProvider]), check in each package's lib
   /// directory for the existence of a `.sdkext` file. This file must contain a
  
positive.code: 
    @override
    Uri restoreAbsolute(Source source) {
      return source.uri;
    }
  
    /// Given a package [name] and a list of folders ([libDirs]),
  
negative.code:     var partUri = new Uri.file(pathos.join(directory, partPath));
      assert(partUri.isAbsolute);
      JavaFile javaFile = new JavaFile.fromUri(partUri);
      return new _SdkExtFileBasedSource(javaFile, importUri);
    }
  
    /// Resolve an import of an sdk extension.
    Source _resolveEntry(Uri libraryEntry, Uri importUri) {
      // Library entry.
      JavaFile javaFile = new JavaFile.fromUri(libraryEntry);
      return new _SdkExtFileBasedSource(javaFile, importUri);
    }
  
    @override
  