Revert of Revert of Move service_discovery_client_impl.* into chrome/common.

chrome/chrome_common.gypi

 # Copyright (c) 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.
 
 {
   'targets': [
     {
       'target_name': 'common',
       'type': 'static_library',
       'variables': {
@@ skipping 222 matching lines @@
         'common/importer/importer_url_row.h',
         'common/importer/profile_import_process_messages.cc',
         'common/importer/profile_import_process_messages.h',
         'common/importer/safari_importer_utils.h',
         'common/importer/safari_importer_utils.mm',
         'common/instant_restricted_id_cache.h',
         'common/instant_types.cc',
         'common/instant_types.h',
         'common/localized_error.cc',
         'common/localized_error.h',
-        'common/local_discovery/service_discovery_client.cc',
-        'common/local_discovery/service_discovery_client.h',
         'common/logging_chrome.cc',
         'common/logging_chrome.h',
         'common/mac/app_mode_common.h',
         'common/mac/app_mode_common.mm',
         'common/mac/cfbundle_blocker.h',
         'common/mac/cfbundle_blocker.mm',
         'common/mac/launchd.h',
         'common/mac/launchd.mm',
         'common/mac/objc_method_swizzle.h',
         'common/mac/objc_method_swizzle.mm',
@@ skipping 164 matching lines @@
           ],
           'include_dirs': [
             '<(DEPTH)/breakpad/src',
           ],
         }],
         ['enable_printing!=0', {
           'dependencies': [
             '<(DEPTH)/printing/printing.gyp:printing',
           ],
         }],
+        ['enable_service_discovery==1', {
+          'sources' : [
+            'common/local_discovery/service_discovery_client.cc',
+            'common/local_discovery/service_discovery_client.h',
+           ]
+        }],
+        ['enable_mdns==1', {
+          'sources' : [
+            'common/local_discovery/service_discovery_client_impl.cc',
+            'common/local_discovery/service_discovery_client_impl.h',
+          ]
+        }],
         ['OS=="android"', {
           'sources/': [
             ['exclude', '^common/chrome_version_info_posix.cc'],
             ['exclude', '^common/importer/'],
             ['include', '^common/importer/imported_favicon_usage.cc$'],
             ['include', '^common/importer/imported_favicon_usage.h$'],
             ['exclude', '^common/service_'],
           ],
           'sources!': [
             'common/badge_util.cc',
@@ skipping 249 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' ],
     },
   ],
 }