Fix some warnings in pub and pkg packages.

pkg/intl/lib/message_lookup_by_library.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.
 
 /**
  * Message/plural format library with locale support. This can have different
  * implementations based on the mechanism for finding the localized versions
  * of messages. This version expects them to be in a library named e.g.
  * 'messages_en_US'. The prefix is set in the [initializeMessages] call, which
  * must be made for a locale before any lookups can be done.
@@ skipping 57 matching lines @@
 /**
  * This provides an abstract class for messages looked up in generated code.
  * Each locale will have a separate subclass of this class with its set of
  * messages. See generate_localized.dart.
  */
 abstract class MessageLookupByLibrary {
   /** Prevent infinite recursion when looking up the message. */
   bool _lookupInProgress = false;
 
   /**
-   * Return true if the locale exists, or if it is null. Null is treated
-   * as meaning that we use the default locale.
-   */
-  bool localeExists(localeName);
-
-  /**
    * Return the localized version of a message. We are passed the original
    * version of the message, which consists of a
    * [message_str] that will be translated, and which may be interpolated
    * based on one or more variables, a [desc] providing a description of usage
    * for the [message_str], and a map of [examples] for each data element to be
    * substituted into the message.
    *
    * For example, if message="Hello, $name", then
    * examples = {'name': 'Sparky'}. If not using the user's default locale, or
    * if the locale is not easily detectable, explicitly pass [locale].
@@ skipping 37 matching lines @@
    * Subclasses should override this to return a list of their message
    * functions.
    */
   Map<String, Function> get messages;
 
   /** Subclasses should override this to return their locale, e.g. 'en_US' */
   String get localeName;
 
   toString() => localeName;
 }