Add assert-in-initializer-list to formal specification.

pkg/analyzer/lib/source/embedder.dart

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+q// 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.
 
 @deprecated
 library analyzer.source.embedder;
 
 import 'dart:collection' show HashMap;
 import 'dart:core';
 import 'dart:io' as io;
 
@@ skipping 164 matching lines @@
   @override
   Uri restoreAbsolute(Source source) {
     String path = source.fullName;
     if (path.length > 3 && path[1] == ':' && path[2] == '\\') {
       path = '/${path[0]}:${path.substring(2).replaceAll('\\', '/')}';
     }
     Source sdkSource = dartSdk.fromFileUri(Uri.parse('file://$path'));
     return sdkSource?.uri;
   }
 }