Use extension-based file picker from CrOS for Aura builds.

chrome/browser/ui/views/shell_dialogs_aura.cc

 // Copyright (c) 2011 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 "chrome/browser/ui/shell_dialogs.h"
 
+#include "chrome/browser/ui/views/file_manager_dialog.h"
+#include "content/browser/browser_thread.h"
+
 // static
 SelectFileDialog* SelectFileDialog::Create(Listener* listener) {
-  return NULL;
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  return new FileManagerDialog(listener);
 }