Componentize TopSites, TopSitesBackend, TopSitesDatabase

components/history/core/test/BUILD.gn

 # 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.
 
 static_library("test") {
   testonly = true
   sources = [
+    "database_test_utils.cc",
+    "database_test_utils.h",
     "history_client_fake_bookmarks.cc",
     "history_client_fake_bookmarks.h",
     "history_unittest_base.cc",
     "history_unittest_base.h",
     "test_history_database.cc",
     "test_history_database.h",
   ]
 
   deps = [
     "//base",
     "//components/history/core/browser",
     "//sql",
     "//testing/gtest",
     "//url",
   ]
 }