Make new StreamController be async by default.

pkg/logging/lib/logging.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Provides APIs for debugging and error logging. This library introduces
  * abstractions similar to those used in other languages, such as the Closure JS
  * Logger and java.util.logging.Logger.
  *
  * ## Installing ##
@@ skipping 178 matching lines @@
 
   /** Log message at level [Level.SEVERE]. */
   void severe(String message) => log(Level.SEVERE, message);
 
   /** Log message at level [Level.SHOUT]. */
   void shout(String message) => log(Level.SHOUT, message);
 
   Stream<LogRecord> _getStream() {
     if (hierarchicalLoggingEnabled || parent == null) {
       if (_controller == null) {
-        _controller = new StreamController<LogRecord>();
+        _controller = new StreamController<LogRecord>(sync: true);
         _stream = _controller.stream.asBroadcastStream();
       }
       return _stream;
     } else {
       return root._getStream();
     }
   }
 
   void _publish(LogRecord record) {
     if (_controller != null) {
@@ skipping 102 matching lines @@
 
   /** Associated exception message (if any) when recording errors messages. */
   String exceptionText;
 
   LogRecord(
       this.level, this.message, this.loggerName,
       [time, this.exception, this.exceptionText]) :
     this.time = (time == null) ? new DateTime.now() : time,
     this.sequenceNumber = LogRecord._nextNumber++;
 }