aura: Fix file-opening functions in platform_util.

chrome/browser/platform_util_linux.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/platform_util.h"
 
-#include <gtk/gtk.h>
-
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/process_util.h"
 #include "base/utf_string_conversions.h"
 #include "content/public/browser/browser_thread.h"
 #include "googleurl/src/gurl.h"
 
 using content::BrowserThread;
 
 namespace {
@@ skipping 62 matching lines @@
 }
 
 void OpenExternal(const GURL& url) {
   if (url.SchemeIs("mailto"))
     XDGEmail(url.spec());
   else
     XDGOpen(url.spec());
 }
 
 }  // namespace platform_util