Add more components to GN build.

components/history.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': [
     {
+      # GN version: //components/history/core/browser
       'target_name': 'history_core_browser',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'dependencies': [
         '../base/base.gyp:base',
         '../net/net.gyp:net',
         '../sql/sql.gyp:sql',
         '../url/url.gyp:url_lib',
         'keyed_service_core',
         'query_parser',
       ],
       'sources': [
+        # Note: sources list duplicated in GN build.
         'history/core/browser/history_client.cc',
         'history/core/browser/history_client.h',
         'history/core/browser/history_match.cc',
         'history/core/browser/history_match.h',
         'history/core/browser/in_memory_database.cc',
         'history/core/browser/in_memory_database.h',
         'history/core/browser/keyword_id.h',
         'history/core/browser/keyword_search_term.cc',
         'history/core/browser/keyword_search_term.h',
         'history/core/browser/url_database.cc',
         'history/core/browser/url_database.h',
         'history/core/browser/url_row.cc',
         'history/core/browser/url_row.h',
       ],
     },
     {
+      # GN version: //components/history/core/common
       'target_name': 'history_core_common',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'dependencies': [
         '../base/base.gyp:base',
       ],
       'sources': [
+        # Note: sources list duplicated in GN build.
         'history/core/common/thumbnail_score.cc',
         'history/core/common/thumbnail_score.h',
       ],
     },
     {
+      # GN version: //components/history/core/test
       'target_name': 'history_core_test_support',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'dependencies': [
         'history_core_browser',
         '../base/base.gyp:base',
         '../url/url.gyp:url_lib',
       ],
       'sources': [
+        # Note: sources list duplicated in GN build.
         'history/core/test/history_client_fake_bookmarks.cc',
         'history/core/test/history_client_fake_bookmarks.h',
       ],
     },
   ],
 }