Refactor ClipboardRecentContent singleton creation.

components/open_from_clipboard.gypi

 # Copyright 2015 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': 'open_from_clipboard',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
         '../url/url.gyp:url_lib',
         'components_strings.gyp:components_strings',
         'omnibox_browser',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
+        'open_from_clipboard/clipboard_recent_content.cc',
         'open_from_clipboard/clipboard_recent_content.h',
         'open_from_clipboard/clipboard_recent_content_ios.h',
         'open_from_clipboard/clipboard_recent_content_ios.mm',
         'open_from_clipboard/clipboard_url_provider.cc',
         'open_from_clipboard/clipboard_url_provider.h',
       ],
     },
   ],
 }