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

components/ntp_snippets/BUILD.gn

Index: components/ntp_snippets/BUILD.gn
diff --git a/components/ntp_snippets/BUILD.gn b/components/ntp_snippets/BUILD.gn
index 8d68dfb31dbac2ef2e0f015414d0a4ac13c01839..e10f4671bfa59b4a852198f87b35ba1ece4f71b3 100644
--- a/components/ntp_snippets/BUILD.gn
+++ b/components/ntp_snippets/BUILD.gn
@@ -18,8 +18,6 @@ static_library("ntp_snippets") {
     "callbacks.h",
     "category.cc",
     "category.h",
-    "category_factory.cc",
-    "category_factory.h",
     "category_info.cc",
     "category_info.h",
     "category_status.cc",
@@ -57,6 +55,9 @@ static_library("ntp_snippets") {
     "remote/remote_suggestions_status_service.h",
     "remote/request_throttler.cc",
     "remote/request_throttler.h",
+    "section_rankers/default_constant_section_ranker.cc",
+    "section_rankers/default_constant_section_ranker.h",
+    "section_rankers/section_ranker.h",
     "sessions/foreign_sessions_suggestions_provider.cc",
     "sessions/foreign_sessions_suggestions_provider.h",
     "sessions/tab_delegate_sync_adapter.cc",
@@ -116,7 +117,6 @@ source_set("unit_tests") {
   testonly = true
   sources = [
     "bookmarks/bookmark_last_visit_utils_unittest.cc",
-    "category_factory_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",