Fix various nits in VM patch files.

runtime/lib/typed_data_patch.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:_internal";
+import "dart:_internal" hide Symbol;
 import "dart:collection" show ListBase;
 import 'dart:math' show Random;
 
 @patch
 class ByteData implements TypedData {
   @patch
   factory ByteData(int length) {
     var list = new Uint8List(length);
     return new _ByteDataView(list, 0, length);
   }
@@ skipping 3045 matching lines @@
         'BYTES_PER_ELEMENT ($alignment)');
   }
 }
 
 int _defaultIfNull(object, value) {
   if (object == null) {
     return value;
   }
   return object;
 }