Convert /** comments to /// in pub.

utils/pub/yaml/visitor.dart

Index: utils/pub/yaml/visitor.dart
diff --git a/utils/pub/yaml/visitor.dart b/utils/pub/yaml/visitor.dart
index 22ada8b2daabdddc3c10632188d2ab90afa32326..737de092bfcbdcf797d200fff80ae2e88021c9cc 100644
--- a/utils/pub/yaml/visitor.dart
+++ b/utils/pub/yaml/visitor.dart
@@ -2,18 +2,18 @@
 // 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.
 
-/** The visitor pattern for YAML documents. */
+/// The visitor pattern for YAML documents. 
 class _Visitor {
-  /** Returns [alias]. */
+  /// Returns [alias]. 
   visitAlias(_AliasNode alias) => alias;
 
-  /** Returns [scalar]. */
+  /// Returns [scalar]. 
   visitScalar(_ScalarNode scalar) => scalar;
 
-  /** Visits each node in [seq] and returns a list of the results. */
+  /// Visits each node in [seq] and returns a list of the results. 
   visitSequence(_SequenceNode seq) => seq.content.map((e) => e.visit(this));
 
-  /** Visits each key and value in [map] and returns a map of the results. */
+  /// Visits each key and value in [map] and returns a map of the results. 
   visitMapping(_MappingNode map) {
     var out = new YamlMap();
     for (var key in map.content.keys) {