Fix inconsistent file error messages.

runtime/bin/file_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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(String name) {
     var file = new File(name);
     _data = [];
     _position = 0;
     file.onError = _reportError;
@@ skipping 401 matching lines @@
   // Constructor for file.
   _File(String this._name);
 
   void exists(void callback(bool exists)) {
     _ensureFileService();
     List request = new List(2);
     request[0] = _FileUtils.kExistsRequest;
     request[1] = _name;
     _fileService.call(request).then((response) {
       if (_isErrorResponse(response)) {
-        _handleErrorResponse(response, "Cannot open file $_name");
+        _handleErrorResponse(response, "Cannot open file '$_name'");
       } else {
         callback(response);
       }
     });
   }
 
   bool existsSync() {
     return _FileUtils.checkedExists(_name);
   }
 
@@ skipping 62 matching lines @@
         mode != FileMode.APPEND) {
       _reportError(new IllegalArgumentException());
       return;
     }
     List request = new List(3);
     request[0] = _FileUtils.kOpenRequest;
     request[1] = _name;
     request[2] = mode._mode;  // Direct int value for serialization.
     _fileService.call(request).then((response) {
       if (_isErrorResponse(response)) {
-        _handleErrorResponse(response, "Cannot open file $_name");
+        _handleErrorResponse(response, "Cannot open file '$_name'");
       } else {
         callback(new _RandomAccessFile(response, _name));
       }
     });
   }
 
   void length(void callback(int length)) {
     _ensureFileService();
     List request = new List(2);
     request[0] = _FileUtils.kLengthFromNameRequest;
@@ skipping 526 matching lines @@
   String _name;
   int _id;
   int _pendingWrites = 0;
 
   SendPort _fileService;
 
   Timer _noPendingWriteTimer;
 
   Function _onNoPendingWrites;
 }