Use precompiled headers for most large projects.

webkit/webkit.gyp

 # Copyright (c) 2010 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.
 
 {
   'includes': [
+    '../build/win_precompile.gypi',
     '../third_party/WebKit/Source/WebKit/chromium/features.gypi',
     'tools/test_shell/test_shell.gypi',
   ],
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'pull_in_webkit_unit_tests',
       'type': 'none',
       'dependencies': [
         '../third_party/WebKit/Source/WebKit/chromium/WebKit.gyp:webkit_unit_tests'
       ],
     },
     {
       'target_name': 'pull_in_DumpRenderTree',
       'type': 'none',
       'dependencies': [
         '../third_party/WebKit/Source/WebKit/chromium/WebKit.gyp:DumpRenderTree'
       ],
     },
   ], # targets
 }