Create a project for maintaining default extensions....

chrome/installer/mini_installer.gyp

 {
   'variables': {
     'version_py': '../../chrome/tools/build/version.py',
     'version_path': '../../chrome/VERSION',
     'lastchange_path': '<(SHARED_INTERMEDIATE_DIR)/build/LASTCHANGE',
     # 'branding_dir' is set in the 'conditions' section at the bottom.
     'msvs_use_common_release': 0,
   },
   'includes': [
     '../../build/common.gypi',
   ],
   'conditions': [
     ['OS=="win"', {
       'targets': [
         {
           'target_name': 'mini_installer',
           'type': 'executable',
           'msvs_guid': '24A5AC7C-280B-4899-9153-6BA570A081E7',
           'dependencies': [
             '../chrome.gyp:chrome',
             '../chrome.gyp:chrome_dll',
+            '../chrome.gyp:default_extensions',
             '../../testing/gtest.gyp:gtest',
             'installer.gyp:setup',
           ],
           'include_dirs': [
             '../..',
             '<(PRODUCT_DIR)',
             '<(INTERMEDIATE_DIR)',
           ],
           'sources': [
             'mini_installer/chrome.release',
@@ skipping 138 matching lines @@
       'variables': {
          'branding_dir': '../app/theme/google_chrome',
       },
     }, { # else branding!="Chrome"
       'variables': {
          'branding_dir': '../app/theme/chromium',
       },
     }],
   ],
 }