Small changes for spec updates/editor suggestions

pkg/intl/lib/src/date_format_field.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.
 
 /**
  * This is a private class internal to DateFormat which is used for formatting
  * particular fields in a template. e.g. if the format is hh:mm:ss then the
  * fields would be "hh", ":", "mm", ":", and "ss". Each type of field knows
  * how to format that portion of a date.
  */
-class _DateFormatField {
+abstract class _DateFormatField {
   /** The format string that defines us, e.g. "hh" */
   String pattern;
 
   /** The DateFormat that we are part of.*/
   DateFormat parent;
 
   _DateFormatField(this.pattern, this.parent);
 
   /**
    * Return the width of [pattern]. Different widths represent different
    * formatting options. See the comment for DateFormat for details.
    */
   int get width => pattern.length;
 
   String fullPattern() => pattern;
 
   String toString() => pattern;
 
   /** Format date according to our specification and return the result. */
   String format(Date date) {
     // Default implementation in the superclass, works for both types of
     // literal patterns, and is overridden by _DateFormatPatternField.
     return pattern;
   }
 
-  abstract void parse(_Stream input, _DateBuilder dateFields);
+  /** Abstract method for subclasses to implementing parsing for their format.*/
+  void parse(_Stream input, _DateBuilder dateFields);
 
   /** Parse a literal field. We just look for the exact input. */
   void parseLiteral(_Stream input) {
     var found = input.read(width);
     if (found != pattern) {
       throwFormatException(input);
     }
   }
 
   /** Throw a format exception with an error message indicating the position.*/
@@ skipping 346 matching lines @@
     var basicString = toBePrinted.toString();
     if (basicString.length >= width) return basicString;
     var buffer = new StringBuffer();
     for (var i = 0; i < width - basicString.length; i++) {
       buffer.add('0');
      }
     buffer.add(basicString);
     return buffer.toString();
   }
 }