Componentize OriginsSeenService & provide iOS factory.

chrome/browser/tab_contents/origins_seen_service.cc

-// 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.
-
-#include "chrome/browser/tab_contents/origins_seen_service.h"
-
-namespace {
-const size_t kDefaultMRUCacheSize = 1000;
-}  // namespace
-
-OriginsSeenService::OriginsSeenService()
-    : origins_seen_(kDefaultMRUCacheSize) {}
-
-OriginsSeenService::~OriginsSeenService() {}
-
-bool OriginsSeenService::Insert(const url::Origin& origin) {
-  bool seen = origins_seen_.Peek(origin) != origins_seen_.end();
-  origins_seen_.Put(origin, true);
-  return seen;
-}