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

components/ntp_snippets/category_factory.h

-// 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.
-
-#ifndef COMPONENTS_NTP_SNIPPETS_CATEGORY_FACTORY_H_
-#define COMPONENTS_NTP_SNIPPETS_CATEGORY_FACTORY_H_
-
-#include <map>
-#include <string>
-#include <vector>
-
-#include "base/macros.h"
-#include "components/ntp_snippets/category.h"
-
-namespace ntp_snippets {
-
-// Creates and orders Category instances.
-class CategoryFactory {
- public:
-  CategoryFactory();
-  ~CategoryFactory();
-
-  // Creates a category from a KnownCategory value. The passed |known_category|
-  // must not be one of the special values (LOCAL_CATEGORIES_COUNT or
-  // REMOTE_CATEGORIES_OFFSET).
-  Category FromKnownCategory(KnownCategories known_category);
-
-  // Creates a category from a category identifier delivered by the server.
-  // |remote_category| must be positive.
-  // Note that remote categories are ordered in the order in which they were
-  // first created by calling this method.
-  Category FromRemoteCategory(int remote_category);
-
-  // Creates a category from an ID as returned by |Category::id()|.
-  // |id| must be a non-negative value.
-  Category FromIDValue(int id);
-
-  // Compares the given categories according to a strict ordering, returning
-  // true if and only if |left| is strictly less than |right|.
-  // This method satisfies the "Compare" contract required by sort algorithms.
-  // The order is determined as follows: All local categories go first, in a
-  // specific order hard-coded in the |CategoryFactory| constructor. All remote
-  // categories follow in the order in which they were first created through
-  // |FromRemoteCategory|.
-  bool CompareCategories(const Category& left, const Category& right) const;
-
- private:
-  bool CategoryExists(int id);
-  void AddKnownCategory(KnownCategories known_category);
-  Category InternalFromID(int id);
-
-  // Stores all known categories in the order which is also returned by
-  // |CompareCategories|.
-  std::vector<Category> ordered_categories_;
-
-  DISALLOW_COPY_AND_ASSIGN(CategoryFactory);
-};
-
-}  // namespace ntp_snippets
-
-#endif  // COMPONENTS_NTP_SNIPPETS_CATEGORY_FACTORY_H_