Fix various nits in VM patch files.

runtime/lib/isolate_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:collection" show HashMap;
-import "dart:_internal";
+import "dart:_internal" hide Symbol;
 
 @patch class ReceivePort {
   @patch factory ReceivePort() = _ReceivePortImpl;
 
   @patch factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) =
       _ReceivePortImpl.fromRawReceivePort;
 }
 
 @patch class Capability {
   @patch factory Capability() = _CapabilityImpl;
@@ skipping 561 matching lines @@
     try {
       return Uri.parse(_getCurrentRootUriStr());
     } catch (e, s) {
       return null;
     }
   }
 
   static String _getCurrentRootUriStr()
       native "Isolate_getCurrentRootUriStr";
 }