Add support for UserIdleTime to Linux.

chrome/chrome_common.gypi

 # Copyright (c) 2009 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.
 
 {
   'target_defaults': {
     'variables': {
       'chrome_common_target': 0,
     },
     'target_conditions': [
@@ skipping 280 matching lines @@
           'dependencies': [
             '../build/linux/system.gyp:gtk',
           ],
           'export_dependent_settings': [
             '../third_party/sqlite/sqlite.gyp:sqlite',
           ],
           'link_settings': {
             'libraries': [
               '-lX11',
               '-lXrender',
+              '-lXss',
               '-lXext',
             ],
           },
         },],
         ['OS=="linux" and selinux==1', {
           'dependencies': [
             '../build/linux/system.gyp:selinux',
           ],
         }],
         ['OS=="mac"', {
@@ skipping 66 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }