Add search_engines and precache components to GN build.

components/precache/precache_defines.gypi

 # Copyright 2013 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': {
+    # These values are duplicated in the GM build in:

[viettrungluu, 2014/07/16 02:53:36]

s/GM/GN/

+    # //components/precache/core:precache_config
     'precache_config_settings_url%': 'http://www.gstatic.com/chrome/wifiprefetch/precache_config',
     'precache_manifest_url_prefix%': 'http://www.gstatic.com/chrome/wifiprefetch/precache_manifest_',
   },
   'conditions': [
     ['precache_config_settings_url != ""', {
       'defines': [
         'PRECACHE_CONFIG_SETTINGS_URL="<(precache_config_settings_url)"',
       ],
     }],
     ['precache_manifest_url_prefix != ""', {
       'defines': [
         'PRECACHE_MANIFEST_URL_PREFIX="<(precache_manifest_url_prefix)"',
       ],
     }],
   ],
 }