Make create_installer_archive.py operate silently by default.

chrome/installer/mini_installer.gypi

 # Copyright (c) 2012 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.
 {
   'dependencies': [
     '<@(chrome_dll_project)',
     '../chrome.gyp:chrome',
     '../chrome.gyp:chrome_nacl_win64',
     '../chrome.gyp:default_extensions',
     '../chrome.gyp:setup',
@@ skipping 203 matching lines @@
         '--resource_file_path=<(INTERMEDIATE_DIR)/packed_files.rc',
         '<(enable_hidpi_flag)',
         '<(target_arch_flag)',
         # TODO(sgk):  may just use environment variables
         #'--distribution=$(CHROMIUM_BUILD)',
         '--distribution=_google_chrome',
         # Optional arguments to generate diff installer
         #'--last_chrome_installer=C:/Temp/base',
         #'--setup_exe_format=DIFF',
         #'--diff_algorithm=COURGETTE',
+        # Optional argument for verbose archiving output.
+        #'--verbose',
       ],
       'message': 'Create installer archive',
     },
   ],
   'conditions': [
     # TODO(mark):  <(branding_dir) should be defined by the
     # global condition block at the bottom of the file, but
     # this doesn't work due to the following issue:
     #
     #   http://code.google.com/p/gyp/issues/detail?id=22
     #
     # Remove this block once the above issue is fixed.
     ['branding == "Chrome"', {
       'variables': {
          'branding_dir': '../app/theme/google_chrome',
       },
     }, { # else branding!="Chrome"
       'variables': {
          'branding_dir': '../app/theme/chromium',
       },
     }],
     ['OS=="win" and buildtype=="Official"', {
       # Optimize for size when doing an official build.
       'optimize' :'size',
     }],
   ],
 }