Remove old default search preferences.

components/search_engines/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.
 
 import("//build/config/features.gni")
 import("//tools/json_to_struct/json_to_struct.gni")
 
 static_library("search_engines") {
   sources = [
     "default_search_manager.cc",
     "default_search_manager.h",
-    "default_search_pref_migration.cc",
-    "default_search_pref_migration.h",
     "keyword_table.cc",
     "keyword_table.h",
     "keyword_web_data_service.cc",
     "keyword_web_data_service.h",
     "search_engine_data_type_controller.cc",
     "search_engine_data_type_controller.h",
     "search_engine_type.h",
     "search_engines_pref_names.cc",
     "search_engines_pref_names.h",
     "search_engines_switches.cc",
@@ skipping 85 matching lines @@
     "//base",
     "//components/sync_preferences:test_support",
     "//testing/gtest",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "default_search_manager_unittest.cc",
-    "default_search_pref_migration_unittest.cc",
     "keyword_table_unittest.cc",
     "search_engine_data_type_controller_unittest.cc",
     "search_host_to_urls_map_unittest.cc",
     "template_url_prepopulate_data_unittest.cc",
     "template_url_service_util_unittest.cc",
     "template_url_unittest.cc",
   ]
 
   deps = [
     ":prepopulated_engines",
@@ skipping 23 matching lines @@
   }
 }
 
 json_to_struct("prepopulated_engines") {
   visibility = [ ":*" ]
 
   source = "prepopulated_engines.json"
   schema_file = "prepopulated_engines_schema.json"
   namespace = "TemplateURLPrepopulateData"
 }