Revert "Change some platform libraries to use `part of URI`."

sdk/lib/developer/profiler.dart

 // Copyright (c) 2014, 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.
 
-part of "dart:developer";
+part of dart.developer;
 
 /// A UserTag can be used to group samples in the Observatory profiler.
 abstract class UserTag {
   /// The maximum number of UserTag instances that can be created by a program.
   static const MAX_USER_TAGS = 64;
 
   external factory UserTag(String label);
 
   /// Label of [this].
   String get label;
@@ skipping 131 matching lines @@
     for (var metric in _metrics.values) {
       metrics.add(metric._toJSON());
     }
     var map = {
       'type': 'MetricList',
       'metrics': metrics,
     };
     return JSON.encode(map);
   }
 }