Use APIs from the latest collection package.

lib/src/runner/parse_metadata.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
+import 'package:collection/collection.dart';
 import 'package:path/path.dart' as p;
 import 'package:source_span/source_span.dart';
 
 import '../backend/metadata.dart';
 import '../backend/platform_selector.dart';
 import '../frontend/timeout.dart';
 import '../util/dart.dart';
 import '../utils.dart';
 
 /// Parse the test metadata for the test file at [path].
@@ skipping 519 matching lines @@
       return fn();
     } on SourceSpanFormatException catch (error) {
       var file = new SourceFile(new File(_path).readAsStringSync(),
           url: p.toUri(_path));
       var span = contextualizeSpan(error.span, literal, file);
       if (span == null) rethrow;
       throw new SourceSpanFormatException(error.message, span);
     }
   }
 }