Move bookmark_model_observer.h to the bookmarks component

components/bookmarks.gypi

 # Copyright 2014 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': 'bookmarks_core_browser',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'dependencies': [
         '../base/base.gyp:base',
         '../ui/base/ui_base.gyp:ui_base',
         '../ui/gfx/gfx.gyp:gfx',
         '../url/url.gyp:url_lib',
       ],
       'sources': [
+        'bookmarks/core/browser/base_bookmark_model_observer.cc',
+        'bookmarks/core/browser/base_bookmark_model_observer.h',
         'bookmarks/core/browser/bookmark_client.h',
         'bookmarks/core/browser/bookmark_match.cc',
         'bookmarks/core/browser/bookmark_match.h',
+        'bookmarks/core/browser/bookmark_model_observer.h',
         'bookmarks/core/browser/bookmark_node.cc',
         'bookmarks/core/browser/bookmark_node.h',
         'bookmarks/core/browser/bookmark_prompt_prefs.cc',
         'bookmarks/core/browser/bookmark_prompt_prefs.h',
         'bookmarks/core/browser/bookmark_service.h',
       ],
     },
     {
       'target_name': 'bookmarks_core_common',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'dependencies': [
         '../base/base.gyp:base',
       ],
       'sources': [
         'bookmarks/core/common/bookmark_constants.cc',
         'bookmarks/core/common/bookmark_constants.h',
         'bookmarks/core/common/bookmark_pref_names.cc',
         'bookmarks/core/common/bookmark_pref_names.h',
       ],
     },
   ],
 }