Fixed parameters losing their original order

pkg/docgen/lib/dart2yaml.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.
 
 /**
  * This library is used to convert data from a map to a YAML string.
  */
 library dart2yaml;
 
+import 'dart:collection';
+
 /**
  * Gets a String representing the input Map in YAML format.
  */
 String getYamlString(Map documentData) {
   StringBuffer yaml = new StringBuffer();
   _addLevel(yaml, documentData, 0);
   return yaml.toString();
 }
 
 /**
  * This recursive function builds a YAML string from [documentData] and
  * adds it to [yaml].
  * The [level] input determines the indentation of the block being processed.
  * The [isList] input determines whether [documentData] is a member of an outer
  * lists of maps. A map must be preceeded with a '-' if it is to exist at the
  * same level of indentation in the YAML output as other members of the list.
  */
 void _addLevel(StringBuffer yaml, Map documentData, int level,
                {bool isList: false}) {
-  // Since the ordering of the keys could be non-deterministic, the keys
-  // are sorted to ensure consistency in the output.
+  // The order of the keys could be nondeterministic, but it is insufficient 
+  // to just sort the keys no matter what, as their order could be significant
+  // (i.e. parameters to a method). The order of the keys should be enforced
+  // by the caller of this function.
   var keys = documentData.keys.toList();
-  keys.sort();
   keys.forEach((key) {
     _calcSpaces(level, yaml);
     // Only the first entry of the map should be preceeded with a '-' since
     // the map is a member of an outer list and the map as a whole must be 
     // marked as a single member of that list. See example 2.4 at
     // http://www.yaml.org/spec/1.2/spec.html#id2759963
     if (isList && key == keys.first) {
       yaml.write("- ");
       level++;
     }
@@ skipping 31 matching lines @@
 
 /**
  * Based on the depth in the file, this function returns the correct spacing
  * for an element in the YAML output.
  */
 void _calcSpaces(int spaceLevel, StringBuffer yaml) {
   for (int i = 0; i < spaceLevel; i++) {
     yaml.write("  ");
   }
 }