dbus: Make it possible to build as shared_library.

dbus/dbus.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'dbus',
-      'type': 'static_library',
+      'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../build/linux/system.gyp:dbus',
         '../third_party/protobuf/protobuf.gyp:protobuf_lite',
       ],
       'export_dependent_settings': [
         '../base/base.gyp:base',
       ],
+      'defines': [
+        'DBUS_IMPLEMENTATION',
+      ],
       'sources': [
         'bus.cc',
         'bus.h',
+        'dbus_export.h',
         'exported_object.cc',
         'exported_object.h',
         'file_descriptor.cc',
         'file_descriptor.h',
         'message.cc',
         'message.h',
         'object_path.cc',
         'object_path.h',
         'object_proxy.cc',
         'object_proxy.h',
@@ skipping 81 matching lines @@
         'test_server.cc',
         'test_service.cc',
         'test_service.h',
       ],
       'include_dirs': [
         '..',
       ],
     },
   ],
 }