Makes PlatformEventSource creation in Env conditional

mojo/examples/launcher/launcher.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdio.h>
 #include <string>
 
 #include "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 277 matching lines @@
   base::FilePath pak_file;
   pak_file = pak_dir.Append(FILE_PATH_LITERAL("ui_test.pak"));
   ui::ResourceBundle::InitSharedInstanceWithPakPath(pak_file);
 
   base::MessageLoop loop;
   mojo::GLES2Initializer gles2;
 
   // TODO(beng): This crashes in a DCHECK on X11 because this thread's
   //             MessageLoop is not of TYPE_UI. I think we need a way to build
   //             Aura that doesn't define platform-specific stuff.
-  aura::Env::CreateInstance();
+  aura::Env::CreateInstance(true);
   mojo::examples::LauncherImpl launcher(shell_handle);
   loop.Run();
 
   return MOJO_RESULT_OK;
 }