Change Platform members to getters instead of methods.

runtime/bin/process_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 _ProcessStartStatus {
   int _errorCode;  // Set to OS error code if process start failed.
   String _errorMessage;  // Set to OS error message if process start failed.
 }
 
 
@@ skipping 37 matching lines @@
       throw new IllegalArgumentException("Arguments is not a List: $arguments");
     }
     int len = arguments.length;
     _arguments = new ObjectArray<String>(len);
     for (int i = 0; i < len; i++) {
       var arg = arguments[i];
       if (arg is !String) {
         throw new IllegalArgumentException("Non-string argument: $arg");
       }
       _arguments[i] = arguments[i];
-      if (Platform.operatingSystem() == 'windows') {
+      if (Platform.operatingSystem == 'windows') {
         _arguments[i] = _windowsArgumentEscape(_arguments[i]);
       }
     }
 
     if (options !== null && options.workingDirectory !== null) {
       _workingDirectory = options.workingDirectory;
       if (_workingDirectory is !String) {
         throw new IllegalArgumentException(
             "WorkingDirectory is not a String: $_workingDirectory");
       }
@@ skipping 351 matching lines @@
   void close() => _process.close();
 
   Process _process;
   Function _callback;
   StringBuffer _stdoutBuffer;
   StringBuffer _stderrBuffer;
   int _exitCode;
   bool _stdoutClosed = false;
   bool _stderrClosed = false;
 }