Enable find-missing-symbols-at-link-time for chromeos builds too.

content/content_browser.gypi

 # Copyright (c) 2012 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../device/vibration/vibration.gyp:device_vibration',
     '../device/vibration/vibration.gyp:device_vibration_mojo_bindings',
@@ skipping 1866 matching lines @@
       ],
       'link_settings': {
         'libraries': [
           '$(SDKROOT)/usr/lib/libbsm.dylib',
         ],
       },
     }],
     ['chromeos==1', {
       'dependencies': [
         '../build/linux/system.gyp:dbus',
+        '../chromeos/chromeos.gyp:chromeos',
         '../chromeos/chromeos.gyp:power_manager_proto',
       ],
       'sources!': [
         'browser/geolocation/wifi_data_provider_linux.cc',
         'browser/power_save_blocker_ozone.cc',
         'browser/power_save_blocker_x11.cc',
       ],
     }],
     ['os_bsd==1', {
       'sources/': [
@@ skipping 66 matching lines @@
         'browser/media/media_web_contents_observer.h',
       ],
     }],
     ['OS == "linux" and use_openssl==1', {
       'dependencies': [
         '../third_party/boringssl/boringssl.gyp:boringssl',
       ],
     }],
   ],
 }