Enable component build for browser_context_keyed_service.

components/browser_context_keyed_service.gypi

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'browser_context_keyed_service',
-      'type': 'static_library',
+      'type': '<(component)',
+      'defines': [
+        'BROWSER_CONTEXT_KEYED_SERVICE_IMPLEMENTATION',
+      ],
       'include_dirs': [
         '..',
       ],
       # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_prefs',
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../content/content.gyp:content_common',
         'user_prefs',
       ],
       'sources': [
+        'browser_context_keyed_service/browser_context_keyed_service_export.h',
         'browser_context_keyed_service/browser_context_dependency_manager.cc',
         'browser_context_keyed_service/browser_context_dependency_manager.h',
         'browser_context_keyed_service/browser_context_keyed_base_factory.h',
         'browser_context_keyed_service/browser_context_keyed_base_factory.cc',
         'browser_context_keyed_service/browser_context_keyed_service.h',
         'browser_context_keyed_service/browser_context_keyed_service_factory.cc',
         'browser_context_keyed_service/browser_context_keyed_service_factory.h',
         'browser_context_keyed_service/dependency_graph.cc',
         'browser_context_keyed_service/dependency_graph.h',
         'browser_context_keyed_service/dependency_node.h',
         'browser_context_keyed_service/refcounted_browser_context_keyed_service.cc',
         'browser_context_keyed_service/refcounted_browser_context_keyed_service.h',
         'browser_context_keyed_service/refcounted_browser_context_keyed_service_factory.cc',
         'browser_context_keyed_service/refcounted_browser_context_keyed_service_factory.h',
       ],
     },
   ],
 }