Fix type checking of void type.

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 223 matching lines @@
       return;
     }
     // TODO(ager): Make the actual kill operation asynchronous.
     if (_kill(_pid, signal._signalNumber)) {
       return;
     }
     _reportError(new ProcessException("Could not kill process"));
     return;
   }
 
-  void _kill(int pid, int signal) native "Process_Kill";
+  bool _kill(int pid, int signal) native "Process_Kill";
 
   void close() {
     if (_closed) {
       throw new ProcessException("Process closed");
     }
     _in.close();
     _out.close();
     _err.close();
     _exitHandler.close();
     _closed = true;
@@ skipping 135 matching lines @@
 
 class _ProcessResult implements ProcessResult {
   const _ProcessResult(int this.exitCode,
                        String this.stdout,
                        String this.stderr);
 
   final int exitCode;
   final String stdout;
   final String stderr;
 }