Mac: Play with using a prefix header.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   'variables': {
     # .gyp files or targets should set chromium_code to 1 if they build
@@ skipping 1152 matching lines @@
             '-Wall',
             '-Wendif-labels',
             '-Wextra',
             # Don't warn about unused function parameters.
             '-Wno-unused-parameter',
             # Don't warn about the "struct foo f = {0};" initialization
             # pattern.
             '-Wno-missing-field-initializers',
           ],
           'conditions': [
-            ['chromium_mac_pch', {'GCC_PRECOMPILE_PREFIX_HEADER': 'YES'},
+            ['chromium_mac_pch', {'GCC_PRECOMPILE_PREFIX_HEADER': 'YES',
+                                  'GCC_PREFIX_HEADER': '/Users/thakis/src/chrome-git/src/build/prefix_header_mac.h'},
                                  {'GCC_PRECOMPILE_PREFIX_HEADER': 'NO'}
             ],
           ],
         },
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
           ['_mac_bundle', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
@@ skipping 233 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: