Linux: fix build with system libevent.

base/base.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     'base.gypi',
@@ skipping 265 matching lines @@
           'dependencies': [
             '../third_party/icu/icu.gyp:icudata',
           ],
           'sources!': [
             'dir_reader_posix_unittest.cc',
             'file_descriptor_shuffle_unittest.cc',
             'threading/worker_pool_posix_unittest.cc',
             'message_pump_libevent_unittest.cc',
           ],
         }, {  # OS != "win"
+          'dependencies': [
+            '../third_party/libevent/libevent.gyp:libevent'
+          ],
           'sources/': [
             ['exclude', '^win/'],
           ],
           'sources!': [
             'debug/trace_event_win_unittest.cc',
             'time_win_unittest.cc',
             'win/win_util_unittest.cc',
           ],
         }],
       ],
@@ skipping 93 matching lines @@
           'msvs_settings': {
             'VCLinkerTool': {
               'SubSystem': '2',         # Set /SUBSYSTEM:WINDOWS
             },
           },
         },
       ],
     }],
   ],
 }