- Fix use of String operator + in runtime and standalone libraries.

runtime/bin/directory_impl.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.
 
 
 // Used for holding error code and error message for failed OS system calls.
 class _OSStatus {
   int _errorCode;
   String _errorMessage;
 }
@@ skipping 64 matching lines @@
   void createTemp(void callback()) {
     _ensureDirectoryService();
     List request = new List(2);
     request[0] = kCreateTempRequest;
     request[1] = _path;
     _directoryService.call(request).receive((result, replyTo) {
       if (result is !List) {
         _path = result;
         callback();
       } else if (_onError != null) {
-        _onError("Could not create temporary directory [$_path]: " +
-                 "${result[1]}");
+        _onError("Could not create temporary directory [$_path]: ${result[1]}");
       }
     });
   }
 
   void createTempSync() {
     var status = new _OSStatus();
     var result = _createTemp(path, status);
     if (result != null) {
       _path = result;
     } else {
       throw new DirectoryException(
-          "Could not create temporary directory [$_path]: " +
+          "Could not create temporary directory [$_path]: "
           "${status._errorMessage}",
           status._errorCode);
     }
   }
 
   void _deleteHelper(bool recursive, String errorMsg, void callback()) {
     _ensureDirectoryService();
     List request = new List(3);
     request[0] = kDeleteRequest;
     request[1] = _path;
@@ skipping 93 matching lines @@
   }
 
   var _onDir;
   var _onFile;
   var _onDone;
   var _onError;
 
   String _path;
   SendPort _directoryService;
 }