Add "Show saved copy" button in dino page when there's offline copy

components/offline_pages/offline_page_model.cc

 // Copyright 2015 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/offline_page_model.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 233 matching lines @@
   std::vector<int64> bookmark_ids;
   for (const auto& id_page_pair : offline_pages_)
     bookmark_ids.push_back(id_page_pair.first);
   DeletePagesByBookmarkId(
       bookmark_ids,
       base::Bind(&OfflinePageModel::OnRemoveAllFilesDoneForClearAll,
                  weak_ptr_factory_.GetWeakPtr(),
                  callback));
 }
 
+bool OfflinePageModel::HasOfflinePages() const {
+  DCHECK(is_loaded_);
+  return !offline_pages_.empty();
+}
+
 const std::vector<OfflinePageItem> OfflinePageModel::GetAllPages() const {
   DCHECK(is_loaded_);
   std::vector<OfflinePageItem> offline_pages;
   for (const auto& id_page_pair : offline_pages_) {
     if (id_page_pair.second.IsMarkedForDeletion())
       continue;
     offline_pages.push_back(id_page_pair.second);
   }
   return offline_pages;
 }
@@ skipping 21 matching lines @@
     const GURL& offline_url) const {
   for (auto iter = offline_pages_.begin();
        iter != offline_pages_.end();
        ++iter) {
     if (iter->second.GetOfflineURL() == offline_url)
       return &(iter->second);
   }
   return nullptr;
 }
 
+const OfflinePageItem* OfflinePageModel::GetPageByOnlineURL(
+    const GURL& online_url) const {
+  for (auto iter = offline_pages_.begin();
+       iter != offline_pages_.end();
+       ++iter) {
+    if (iter->second.url == online_url)
+      return &(iter->second);
+  }
+  return nullptr;
+}
+
 void OfflinePageModel::CheckForExternalFileDeletion() {
   DCHECK(is_loaded_);
 
   std::vector<std::pair<int64, base::FilePath>> id_path_pairs;
   for (const auto& id_page_pair : offline_pages_) {
     id_path_pairs.push_back(
         std::make_pair(id_page_pair.first, id_page_pair.second.file_path));
   }
 
   std::vector<int64>* ids_of_pages_missing_archive_file =
@@ skipping 327 matching lines @@
 }
 
 void OfflinePageModel::CacheLoadedData(
     const std::vector<OfflinePageItem>& offline_pages) {
   offline_pages_.clear();
   for (const auto& offline_page : offline_pages)
     offline_pages_[offline_page.bookmark_id] = offline_page;
 }
 
 }  // namespace offline_pages