Use precompiled headers for most large projects.

content/content.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,  # Use higher warning level.
   },
   'includes': [
+    '../build/win_precompile.gypi',
     'content_app.gypi',
     'content_browser.gypi',
     'content_common.gypi',
     'content_gpu.gypi',
     'content_plugin.gypi',
     'content_ppapi_plugin.gypi',
     'content_renderer.gypi',
     'content_tests.gypi',
     'content_utility.gypi',
     'content_worker.gypi',
   ],
 }