Updated observatory_pub_packages dependency

runtime/observatory/lib/tracer.dart

 // Copyright (c) 2013, 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.
 
 library tracer;
 
 import 'dart:async';
 
 import 'package:logging/logging.dart';
-import 'package:observe/observe.dart';
 
 _deepCopy(src) {
   if (src is Map) {
     var dest = {};
     src.forEach((key, val) {
       dest[key] = _deepCopy(val);
     });
     return dest;
   } else if (src is List) {
     var dest = [];
@@ skipping 15 matching lines @@
 
   String toString() {
     return "[${timeStamp}] ${message}";
   }
 
   int _time;
   String message;
   Map map;
 }
 
-class Tracer extends Observable {
+class Tracer {
   // The current global tracer.
   static Tracer get current => _current;
 
   static Tracer _current;
 
   static void start() {
     if (_current == null) {
       _current = new Tracer();
     }
   }
 
   static void stop() {
     if (_current != null) {
       _current.cancel();
       _current = null;
     }
   }
 
   // The tracer subscribes to all logging events.
   StreamSubscription loggerSub = null;
 
   // The start time for the current request.
   Stopwatch _time;
 
   // A list of all tracing events for thre current request.
-  ObservableList<TraceEvent> events = new ObservableList<TraceEvent>();
+  List<TraceEvent> events = <TraceEvent>[];
 
   Tracer() {
     _time = new Stopwatch();
     _time.start();
     loggerSub = Logger.root.onRecord.listen((LogRecord rec) {
       // Echo all log messages to the trace.
       trace('${rec.level.name}: ${rec.message}');
     });
     reset();
   }
 
   void cancel() {
     loggerSub.cancel();
   }
 
   void reset() {
     _time.reset();
     events.clear();
   }
 
   TraceEvent trace(String message, {Map map: null}) {
     var event = new TraceEvent.msg(_time.elapsedMicroseconds, message, map);
     events.add(event);
     return event;
   }
 }