Add an implementation for async_network_alive to Linux

chrome/chrome.gyp

 # Copyright (c) 2010 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.
 
 {
   'variables': {
     'chromium_code': 1,
 
     'variables': {
       'version_py_path': 'tools/build/version.py',
@@ skipping 716 matching lines @@
       ],
     },
     {
       'target_name': 'notifier',
       'type': '<(library)',
       'sources': [
         'browser/sync/notifier/base/async_dns_lookup.cc',
         'browser/sync/notifier/base/async_dns_lookup.h',
         'browser/sync/notifier/base/async_network_alive.h',
         'browser/sync/notifier/base/fastalloc.h',
-        'browser/sync/notifier/base/linux/network_status_detector_task_linux.cc',
+        'browser/sync/notifier/base/linux/async_network_alive_linux.cc',
         'browser/sync/notifier/base/mac/network_status_detector_task_mac.h',
         'browser/sync/notifier/base/mac/network_status_detector_task_mac.cc',
         'browser/sync/notifier/base/nethelpers.cc',
         'browser/sync/notifier/base/nethelpers.h',
         'browser/sync/notifier/base/network_status_detector_task.cc',
         'browser/sync/notifier/base/network_status_detector_task.h',
         'browser/sync/notifier/base/network_status_detector_task_mt.cc',
         'browser/sync/notifier/base/network_status_detector_task_mt.h',
         'browser/sync/notifier/base/posix/time_posix.cc',
         'browser/sync/notifier/base/signal_thread_task.h',
@@ skipping 68 matching lines @@
         '_USE_32BIT_TIME_T',
         'kXmppProductName="chromium-sync"',
       ],
       'dependencies': [
         '../third_party/expat/expat.gyp:expat',
         '../third_party/libjingle/libjingle.gyp:libjingle',
         'sync_proto',
       ],
       'conditions': [
         ['OS=="linux"', {
-          'sources!': [
-            'browser/sync/notifier/base/network_status_detector_task_mt.cc',
-          ],
           'dependencies': [
             '../build/linux/system.gyp:gtk'
           ],
         }],
       ],
     },
     {
       'target_name': 'sync',
       'type': '<(library)',
       'sources': [
@@ skipping 758 matching lines @@
       }],  # targets
     }],  # OS=="linux" or OS=="freebsd"
   ],  # 'conditions'
 }
 
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