Fixed interface documentation

runtime/observatory/lib/src/models/objects/source_location.dart

 // Copyright (c) 2016, 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.
 
 part of models;
 
 abstract class Location {
   /// The script containing the source location.
   ScriptRef get script;
 
-  /// The last token of the location if this is a range. [optional]
+  /// [optional] The first token of the location.
   int get tokenPos;
 }
 
 abstract class SourceLocation implements Location {
-  /// The last token of the location if this is a range.
+  /// The first token of the location.
   int get tokenPos;
 
-  /// The last token of the location if this is a range. [optional]
+  /// [optional] The last token of the location if this is a range.
   int get endTokenPos;
 }
 
 abstract class UnresolvedSourceLocation implements Location {
-  // [optional] The uri of the script containing the source location if the
-  // script has yet to be loaded.
+  /// [optional] The uri of the script containing the source location if the
+  /// script has yet to be loaded.
   String get scriptUri;
 
   /// [optional] An approximate line number for the source location. This may
   /// change when the location is resolved.
   int get line;
 
   /// [optional] An approximate column number for the source location. This may
   /// change when the location is resolved.
   int get column;
 }