[Offline Pages] Remove load state from public OfflinePageModel API.

components/offline_pages/core/stub_offline_page_model.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 "components/offline_pages/core/stub_offline_page_model.h"
 
 namespace offline_pages {
 
 StubOfflinePageModel::StubOfflinePageModel() {}
 StubOfflinePageModel::~StubOfflinePageModel() {}
@@ skipping 31 matching lines @@
 void StubOfflinePageModel::GetPageByOfflineId(
     int64_t offline_id,
     const SingleOfflinePageItemCallback& callback) {}
 void StubOfflinePageModel::GetPagesByURL(
     const GURL& url,
     URLSearchMode url_search_mode,
     const MultipleOfflinePageItemCallback& callback) {}
 ClientPolicyController* StubOfflinePageModel::GetPolicyController() {
   return &policy_controller_;
 }
-bool StubOfflinePageModel::is_loaded() const {
-  return true;
-}
 OfflineEventLogger* StubOfflinePageModel::GetLogger() {
   return nullptr;
 }
 }  // namespace offline_pages