anchor.diff:    }
   
     void compileFromKernel(Uri rootLibraryUri, Iterable<Uri> libraries) {
  +    _userCodeLocations.add(new CodeLocation(rootLibraryUri));
       selfTask.measureSubtask("compileFromKernel", () {
         JClosedWorld closedWorld = selfTask.measureSubtask("computeClosedWorld",
             () => computeClosedWorld(rootLibraryUri, libraries));
  
positive.code:         return;
        }
        if (options.cfeOnly) return;
        _mainLibraryUri = result.rootLibraryUri;
  
        frontendStrategy.registerLoadedLibraries(result);
        for (Uri uri in result.libraries) {
  
negative.code:     if (element == null) return assumeInUserCode;
      Uri libraryUri = _uriFromElement(element);
      if (libraryUri == null) return false;
      if (_userCodeLocations.isEmpty && assumeInUserCode) return true;
      return _userCodeLocations.any(
          (CodeLocation codeLocation) => codeLocation.inSameLocation(libraryUri));
    }
  
    /// Return a canonical URI for the source of [element].
  