Adding the option to drop in a new BrowserDistribution instance for experimen...

build/common.gypi

 # Copyright (c) 2009 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': {
     # .gyp files should set chromium_code to 1 if they build Chromium-specific
     # code, as opposed to external code.  This variable is used to control
     # such things as the set of warnings to enable, and whether warnings are
     # treated as errors.
@@ skipping 54 matching lines @@
     # To do a shared build on linux we need to be able to choose between type
     # static_library and shared_library. We default to doing a static build
     # but you can override this with "gyp -Dlibrary=shared_library" or you
     # can add the following line (without the #) to ~/.gyp/include.gypi
     # {'variables': {'library': 'shared_library'}}
     # to compile as shared by default
     'library%': 'static_library',
     
     # The Google Update appid.
     'google_update_appid%': '{8A69D345-D564-463c-AFF1-A69D9E530F96}',
+    
+    # Extra defines to add to built targets
+    'extra_custom_defines%': [],
 
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to prevent release.vsprops from being included.
     # Yes(1) means include release.vsprops.
     # Once all vsprops settings are migrated into gyp, this can go away.
     'msvs_use_common_release%': 1,
 
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to override additional linker options for msvs.
     # Yes(1) means set use the common linker options.
@@ skipping 77 matching lines @@
           }],
         ],
       }],
     ],
   },
   'target_defaults': {
     'variables': {
       'mac_release_optimization%': '3', # Use -O3 unless overridden
       'mac_debug_optimization%': '0'    # Use -O0 unless overridden
     },
+    'defines': [
+      '<@(extra_custom_defines)',
+    ],
     'conditions': [
       ['branding=="Chrome"', {
         'defines': ['GOOGLE_CHROME_BUILD'],
       }, {  # else: branding!="Chrome"
         'defines': ['CHROMIUM_BUILD'],
       }],
       ['toolkit_views==1', {
         'defines': ['TOOLKIT_VIEWS=1'],
       }],
       ['chromeos==1', {
@@ skipping 589 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }