Adding an Android about:flags feature for offline previews

components/previews/core/BUILD.gn

 # Copyright 2016 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("core") {
   sources = [
     "previews_black_list.cc",
     "previews_black_list.h",
     "previews_black_list_item.cc",
     "previews_black_list_item.h",
     "previews_decider.h",
     "previews_experiments.cc",
     "previews_experiments.h",
+    "previews_features.cc",
+    "previews_features.h",
     "previews_io_data.cc",
     "previews_io_data.h",
     "previews_opt_out_store.h",
     "previews_opt_out_store_sql.cc",
     "previews_opt_out_store_sql.h",
     "previews_ui_service.cc",
     "previews_ui_service.h",
   ]
 
   deps = [
@@ skipping 22 matching lines @@
     "//base/test:test_support",
     "//components/variations",
     "//net:net",
     "//net:test_support",
     "//sql",
     "//sql:test_support",
     "//testing/gtest",
     "//url:url",
   ]
 }