x11: Include X11 dependencies only when building with X11.

content/content_plugin.gypi

 # 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.
 
 {
   'conditions': [
     ['enable_plugins==1', {
       'dependencies': [
         '../skia/skia.gyp:skia',
         '../third_party/npapi/npapi.gyp:npapi',
@@ skipping 38 matching lines @@
         ['toolkit_uses_gtk == 1', {
           'dependencies': [
             '../build/linux/system.gyp:gtk',
           ],
           'link_settings': {
             'libraries': [
               '-lXext',
             ],
           },
         }],
-        ['use_aura==1 and OS!="win"', {
+        ['use_x11 == 1', {
           'link_settings': {
             'libraries': [
               '-lXext',
             ],
           },
         }],
       ],
     }],
   ],
 }