Source in string_buffer from runtime.

dart/frog/leg/lib/mockimpl.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.
 
 // Mocks of classes and interfaces that Leg cannot read directly.
 
 // TODO(ahe): Remove this file.
 
 class JSSyntaxRegExp implements RegExp {
   JSSyntaxRegExp(String pattern,
                  [bool multiLine = false,
                   bool ignoreCase = false]) {
     throw 'JSSyntaxRegExp is not implemented';
   }
 }
 
-class StringBufferImpl {
-  StringBufferImpl([content]) {
-    throw 'StringBufferImpl is not implemented';
-  }
-}
-
 class ReceivePortFactory {
   factory ReceivePort() {
     throw 'factory ReceivePort is not implemented';
   }
 
   factory ReceivePort.singleShot() {
     throw 'factory ReceivePort.singleShot is not implemented';
   }
 }
 
@@ skipping 239 matching lines @@
     }
     String twoDigitMinutes =
         twoDigits(inMinutes.remainder(Duration.MINUTES_PER_HOUR));
     String twoDigitSeconds =
         twoDigits(inSeconds.remainder(Duration.SECONDS_PER_MINUTE));
     String threeDigitMs =
         threeDigits(inMilliseconds.remainder(Duration.MILLISECONDS_PER_SECOND));
     return "${inHours}:${twoDigitMinutes}:${twoDigitSeconds}.${threeDigitMs}";
   }
 }