New build flag system, convert Google Now flag

chrome/chrome_child.gypi

 # Copyright 2015 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.
 
 {
   'targets': [
     {
       'target_name': 'child',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
       'dependencies': [
+        'chrome_common_features',
         '../base/base.gyp:base',
         '../content/content.gyp:content_child',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'child/pdf_child_init.cc',
         'child/pdf_child_init.h',
       ],
     },
   ],
 }