[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..324bffa8e0eddc3acb0fad9b60caeaea2a6c65f8 100644
--- a/components/ntp_snippets/category.cc
+++ b/components/ntp_snippets/category.cc
@@ -16,6 +16,27 @@ bool Category::IsKnownCategory(KnownCategories known_category) const {
   return id_ == static_cast<int>(known_category);
 }
 
+// static
+Category Category::FromKnownCategory(KnownCategories known_category) {
+  const int id = static_cast<int>(known_category);

[Marc Treib, 2016/12/13 12:22:42]

nit: just inline into the return

[vitaliii, 2016/12/14 08:59:38]

Done.

+  return FromIDValue(id);
+}
+
+// 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);
+}
+
 bool operator==(const Category& left, const Category& right) {
   return left.id() == right.id();
 }