components: Extract pref_registry component out of user_prefs.

components/user_prefs.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': 'pref_registry',
+      'type': '<(component)',
+      'dependencies': [
+        '../base/base.gyp:base',
+        '../base/base.gyp:base_prefs',
+        '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
+        '../ui/base/ui_base.gyp:ui_base',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+      'defines': [
+        'PREF_REGISTRY_IMPLEMENTATION',
+      ],
+      'sources': [
+        'user_prefs/pref_registry_syncable.cc',
+        'user_prefs/pref_registry_syncable.h',
+        'user_prefs/pref_registry_export.h',
+      ],
+    },
+    {
       'target_name': 'user_prefs',
       'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_prefs',
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../content/content.gyp:content_browser',
         '../ui/base/ui_base.gyp:ui_base',
       ],
       'include_dirs': [
         '..',
       ],
       'defines': [
         'USER_PREFS_IMPLEMENTATION',
       ],
       'sources': [
-        'user_prefs/pref_registry_syncable.cc',
-        'user_prefs/pref_registry_syncable.h',
         'user_prefs/user_prefs.cc',
         'user_prefs/user_prefs.h',
         'user_prefs/user_prefs_export.h',
       ],
     },
   ],
 }