Move extension_messages.h to extensions/common.

extensions/extensions.gyp

 # Copyright 2013 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': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 31 matching lines @@
         'common/event_filter.h',
         'common/event_filtering_info.cc',
         'common/event_filtering_info.h',
         'common/event_matcher.cc',
         'common/event_matcher.h',
         'common/extension.cc',
         'common/extension.h',
         'common/extension_api.cc',
         'common/extension_api.h',
         'common/extension_api_stub.cc',
+        'common/extension_message_generator.cc',
+        'common/extension_message_generator.h',
+        'common/extension_messages.cc',
+        'common/extension_messages.h',
         'common/extension_paths.cc',
         'common/extension_paths.h',
         'common/extension_resource.cc',
         'common/extension_resource.h',
         'common/extension_set.cc',
         'common/extension_set.h',
         'common/extension_urls.cc',
         'common/extension_urls.h',
         'common/extensions_client.cc',
         'common/extensions_client.h',
@@ skipping 261 matching lines @@
         'common/test_util.cc',
         'common/test_util.h',
         'common/value_builder.cc',
         'common/value_builder.h',
       ],
       # Disable c4267 warnings until we fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
     },
   ]
 }