Clean up some warnings and deprecated calls.

utils/tests/pub/command_line_config.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.
 
 library command_line_config;
 
 import 'dart:io';
 
 import '../../../pkg/path/lib/path.dart' as path;
 import '../../../pkg/unittest/lib/unittest.dart';
@@ skipping 98 matching lines @@
     for (var i = 0; i < length - string.length; i++) {
       result.add(' ');
     }
 
     return result.toString();
   }
 
   String _indent(String str) {
     // TODO(nweiz): Use this simpler code once issue 2980 is fixed.
     // return str.replaceAll(new RegExp("^", multiLine: true), "  ");
-    return Strings.join(str.split("\n").map((line) => "  $line"), "\n");
+    return str.split("\n").map((line) => "  $line").join("\n");
   }
 }
 
 class _StackFrame {
   static final fileRegExp = new RegExp(
       r'#\d+\s+(.*) \(file://(/.+):(\d+):(\d+)\)');
   static final coreRegExp = new RegExp(r'#\d+\s+(.*) \((.+):(\d+):(\d+)\)');
 
   /// If `true`, then this stack frame is for a library built into Dart and
   /// not a regular file path.
@@ skipping 29 matching lines @@
     var library = match[2];
     if (!isCore) {
       // Make the library path relative to the entrypoint.
       library = path.relative(library);
     }
 
     var member = match[1].replaceAll("<anonymous closure>", _lambda);
     return new _StackFrame._(isCore, library, match[3], match[4], member);
   }
 }