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

components/ntp_snippets/category.cc

Index: components/ntp_snippets/category.cc
diff --git a/components/ntp_snippets/category.cc b/components/ntp_snippets/category.cc
index abc86ab9f2c71827710d8f2d477ec9206c170991..4409ac1b376b7491129f46ece2c591e1ae30edd5 100644
--- a/components/ntp_snippets/category.cc
+++ b/components/ntp_snippets/category.cc
@@ -8,6 +8,26 @@
 
 namespace ntp_snippets {
 
+// static
+Category Category::FromKnownCategory(KnownCategories known_category) {
+  return FromIDValue(static_cast<int>(known_category));
+}
+
+// static
+Category Category::FromRemoteCategory(int remote_category) {
+  DCHECK_GT(remote_category, 0);
+  return Category(static_cast<int>(KnownCategories::REMOTE_CATEGORIES_OFFSET) +
+                  remote_category);
+}
+
+// static
+Category Category::FromIDValue(int id) {
+  DCHECK_GE(id, 0);
+  DCHECK(id < static_cast<int>(KnownCategories::LOCAL_CATEGORIES_COUNT) ||
+         id > static_cast<int>(KnownCategories::REMOTE_CATEGORIES_OFFSET));
+  return Category(id);
+}
+
 Category::Category(int id) : id_(id) {}
 
 bool Category::IsKnownCategory(KnownCategories known_category) const {