Moves shared history test helpers into util classes.

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",
     "fake_web_history_service.cc",
     "fake_web_history_service.h",
     "history_backend_db_base_test.cc",
     "history_backend_db_base_test.h",
     "history_client_fake_bookmarks.cc",
     "history_client_fake_bookmarks.h",
+    "history_service_test_util.cc",
+    "history_service_test_util.h",
     "history_unittest_base.cc",
     "history_unittest_base.h",
     "test_history_database.cc",
     "test_history_database.h",
     "thumbnail-inl.h",
     "thumbnail.cc",
     "thumbnail.h",
     "thumbnail_ios.mm",
     "wait_top_sites_loaded_observer.cc",
     "wait_top_sites_loaded_observer.h",
   ]
 
   deps = [
     "//base",
     "//components/history/core/browser",
     "//net",
     "//sql",
     "//sql:test_support",
     "//testing/gtest",
     "//ui/gfx",
     "//url",
   ]
 
   if (is_ios) {
     sources -= [ "thumbnail.cc" ]
   }
 }