Generate param traits even when shared by mutliple message files.

chrome/chrome_common.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.
 
 {
   'targets': [
     {
       'target_name': 'common',
       'type': 'static_library',
       'variables': {
@@ skipping 81 matching lines @@
         'common/cloud_print/cloud_print_class_mac.h',
         'common/cloud_print/cloud_print_class_mac.mm',
         'common/cloud_print/cloud_print_helpers.cc',
         'common/cloud_print/cloud_print_helpers.h',
         'common/cloud_print/cloud_print_proxy_info.cc',
         'common/cloud_print/cloud_print_proxy_info.h',
         'common/common_message_generator.cc',
         'common/common_message_generator.h',
         'common/common_param_traits.cc',
         'common/common_param_traits.h',
+        'common/common_param_traits_macros.h',
         'common/content_settings.cc',
         'common/content_settings.h',
         'common/content_settings_helper.cc',
         'common/content_settings_helper.h',
         'common/content_settings_pattern.cc',
         'common/content_settings_pattern.h',
         'common/content_settings_pattern_parser.cc',
         'common/content_settings_pattern_parser.h',
         'common/content_settings_types.h',
         'common/custom_handlers/protocol_handler.cc',
@@ skipping 415 matching lines @@
         'common/metrics/proto/user_action_event.proto',
       ],
       'variables': {
         'proto_in_dir': 'common/metrics/proto',
         'proto_out_dir': 'chrome/common/metrics/proto',
       },
       'includes': [ '../build/protoc.gypi' ],
     },
   ],
 }