fix warning in Logger

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.
  */
 #library('logging');
@@ skipping 73 matching lines @@
    */
   Level get level {
     if (hierarchicalLoggingEnabled) {
       if (_level != null) return _level;
       if (parent != null) return parent.level;
     }
     return _rootLevel;
   }
 
   /** Override the level for this particular [Logger] and its children. */
-  Level set level(value) {
+  set level(value) {
     if (hierarchicalLoggingEnabled && parent != null) {
       _level = value;
     } else {
       if (parent != null) {
         throw new UnsupportedOperationException(
             'Please set "hierarchicalLoggingEnabled" to true if you want to '
             'change the level on a non-root logger.');
       }
       _rootLevel = value;
     }
@@ skipping 220 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 Date.now() : time,
     this.sequenceNumber = LogRecord._nextNumber++;
 }