Fix various nits in VM patch files.

runtime/lib/string_buffer_patch.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.
 
+import 'dart:typed_data' show Uint16List;
+
 @patch class StringBuffer {
   static const int _BUFFER_SIZE = 64;
   static const int _PARTS_TO_COMPACT = 128;
   static const int _PARTS_TO_COMPACT_SIZE_LIMIT = _PARTS_TO_COMPACT * 8;
 
   /**
    * When strings are written to the string buffer, we add them to a
    * list of string parts.
    */
   List<String> _parts;
@@ skipping 161 matching lines @@
     _partsCodeUnitsSinceCompaction = 0;
     _partsCompactionIndex = _parts.length;
   }
 
   /**
    * Create a [String] from the UFT-16 code units in buffer.
    */
   static String _create(Uint16List buffer, int length, bool isLatin1)
       native "StringBuffer_createStringFromUint16Array";
 }