Make the implementation .cc files go away, instead have the authors give us a...

chrome/chrome_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.
 
 {
   'target_defaults': {
     'variables': {
       'chrome_common_target': 0,
     },
     'target_conditions': [
@@ skipping 28 matching lines @@
           'common/child_process_logging_mac.mm',
           'common/child_process_logging_win.cc',
           'common/child_thread.cc',
           'common/child_thread.h',
           'common/chrome_application_mac.h',
           'common/chrome_application_mac.mm',
           'common/chrome_counters.cc',
           'common/chrome_counters.h',
           'common/chrome_version_info.cc',
           'common/chrome_version_info.h',
+          'common/common_message_generator.cc',
           'common/common_param_traits.cc',
           'common/common_param_traits.h',
           'common/content_restriction.h',
           'common/content_settings.cc',
           'common/content_settings.h',
           'common/content_settings_helper.cc',
           'common/content_settings_helper.h',
           'common/content_settings_types.h',
           'common/database_messages.cc',
           'common/database_messages.h',
@@ skipping 576 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }