Revert 45783

sdk/lib/profiler/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.
 
 /// Instrument your code with counters, gauges, and more.
-part of dart.developer;
+library dart.profiler;
+
+import 'dart:convert';
 
 /// 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;
 
   factory UserTag(String label) => new _FakeUserTag(label);
 
   /// Label of [this].
   String get label;
@@ skipping 172 matching lines @@
     for (var metric in _metrics.values) {
       metrics.add(metric._toJSON());
     }
     var map = {
       'type': 'MetricList',
       'metrics': metrics,
     };
     return JSON.encode(map);
   }
 }