Fix 'Unused local variable' hints in analyzer and analysis_server.

pkg/analyzer/bin/formatter.dart

 #!/usr/bin/env 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.
 
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:args/args.dart';
@@ skipping 136 matching lines @@
 _formatDirectory(dir) => dir.listSync(followLinks: FOLLOW_LINKS)
     .forEach((resource) => _formatResource(resource));
 
 _formatFile(file) {
   if (_isDartFile(file)) {
     if (_isPatchFile(file) && !paths.contains(file.path)) {
       _log('Skipping patch file "${file.path}"');
       return;
     }
     try {
-      var buffer = new StringBuffer();
       var rawSource = file.readAsStringSync();
       var formatted = _format(rawSource, CodeKind.COMPILATION_UNIT);
       if (overwriteFileContents) {
         // Only touch files files whose contents will be changed
         if (rawSource != formatted) {
           file.writeAsStringSync(formatted);
         }
       } else {
         print(formatted);
       }
@@ skipping 83 matching lines @@
                      'offset': formatResult.selection.offset,
                      'length': formatResult.selection.length
                   }
     });
 
 /// Log the given [msg].
 _log(String msg) {
   //TODO(pquitslund): add proper log support
   print(msg);
 }