[NTP::SectionOrder] Replace CategoryFactory with a category ranker.

components/ntp_snippets/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/ui.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
 
 static_library("ntp_snippets") {
   sources = [
     "bookmarks/bookmark_last_visit_utils.cc",
     "bookmarks/bookmark_last_visit_utils.h",
     "bookmarks/bookmark_suggestions_provider.cc",
     "bookmarks/bookmark_suggestions_provider.h",
     "callbacks.h",
     "category.cc",
     "category.h",
-    "category_factory.cc",
-    "category_factory.h",
     "category_info.cc",
     "category_info.h",
+    "category_rankers/category_ranker.h",
+    "category_rankers/constant_category_ranker.cc",
+    "category_rankers/constant_category_ranker.h",
     "category_status.cc",
     "category_status.h",
     "content_suggestion.cc",
     "content_suggestion.h",
     "content_suggestions_metrics.cc",
     "content_suggestions_metrics.h",
     "content_suggestions_provider.cc",
     "content_suggestions_provider.h",
     "content_suggestions_service.cc",
     "content_suggestions_service.h",
@@ skipping 74 matching lines @@
       "category_info.h",
       "category_status.h",
     ]
   }
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "bookmarks/bookmark_last_visit_utils_unittest.cc",
-    "category_factory_unittest.cc",
+    "category_rankers/constant_category_ranker_unittest.cc",
+    "category_unittest.cc",
     "content_suggestions_service_unittest.cc",
     "offline_pages/recent_tab_suggestions_provider_unittest.cc",
     "physical_web_pages/physical_web_page_suggestions_provider_unittest.cc",
     "remote/ntp_snippet_unittest.cc",
     "remote/ntp_snippets_fetcher_unittest.cc",
     "remote/remote_suggestions_database_unittest.cc",
     "remote/remote_suggestions_provider_unittest.cc",
     "remote/remote_suggestions_status_service_unittest.cc",
     "remote/request_throttler_unittest.cc",
     "remote/test_utils.cc",
@@ skipping 25 matching lines @@
     "//net:test_support",
     "//testing/gtest",
     "//third_party/icu/",
     "//ui/gfx:test_support",
   ]
 }
 
 source_set("test_support") {
   testonly = true
   sources = [
+    "category_rankers/mock_category_ranker.cc",
+    "category_rankers/mock_category_ranker.h",
     "mock_content_suggestions_provider_observer.cc",
     "mock_content_suggestions_provider_observer.h",
     "offline_pages/offline_pages_test_utils.cc",
     "offline_pages/offline_pages_test_utils.h",
   ]
 
   deps = [
     ":ntp_snippets",
     "//base",
     "//components/offline_pages/core",
     "//components/offline_pages/core:test_support",
     "//testing/gmock",
   ]
 }