Componentize OriginsSeenService & provide iOS factory.

chrome/browser/tab_contents/origins_seen_service.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 CHROME_BROWSER_TAB_CONTENTS_ORIGINS_SEEN_SERVICE_H_
-#define CHROME_BROWSER_TAB_CONTENTS_ORIGINS_SEEN_SERVICE_H_
-
-#include "base/containers/mru_cache.h"
-#include "components/keyed_service/core/keyed_service.h"
-#include "url/origin.h"
-
-class OriginsSeenService : public KeyedService {
- public:
-  OriginsSeenService();
-  ~OriginsSeenService() override;
-
-  // Used when deciding whether or not to record
-  // Navigation.SchemePerUniqueOrigin[OTR]. Inserts a copy of |origin| into the
-  // set |origins_seen_|, and returns whether or not |origin| was already in the
-  // set.
-  bool Insert(const url::Origin& origin);
-
- private:
-  // Used by |HaveAlreadySeenOrigin|. This cache is in volatile storage because
-  // Off The Record Profiles also use this Service.
-  base::MRUCache<url::Origin, bool> origins_seen_;
-};
-
-#endif  // CHROME_BROWSER_TAB_CONTENTS_ORIGINS_SEEN_SERVICE_H_