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 5a9894a0aaee0c34d53f9ff3996645dd56ff942d..1d6282ae9c638713312659dc295f3c328ef0337c 100644
--- a/utils/pub/yaml/visitor.dart
+++ b/utils/pub/yaml/visitor.dart
@@ -4,18 +4,18 @@
 
 part of yaml;
 
-/** 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) {