Last_n: do not delete the currently loading offline snapshot.

chrome/browser/android/offline_pages/recent_tab_helper.cc

 // Copyright (c) 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/android/offline_pages/recent_tab_helper.h"
 
 #include <queue>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 194 matching lines @@
            << web_contents()->GetLastCommittedURL().spec();
 
   // If there is an ongoing downloads request, lets make Background Offliner
   // take over downloading that page.
   if (downloads_ongoing_snapshot_info_) {
     DVLOG(1) << " - Passing ongoing downloads request to Background Offliner";
     ReportDownloadStatusToRequestCoordinator(
         downloads_ongoing_snapshot_info_.get(), false);
   }
 
-  // If the previous page was saved, delete it now.
-  if (last_n_latest_saved_snapshot_info_) {
+  // If currently loading an offline page get a pointer to it. It will be null
+  // otherwise.
+  const OfflinePageItem* current_offline_page =
+      OfflinePageUtils::GetOfflinePageFromWebContents(web_contents());
+
+  // If the previous page was saved, delete it now unless we are currently
+  // loading that very snapshot.
+  if (last_n_latest_saved_snapshot_info_ &&
+      (!current_offline_page ||
+       current_offline_page->offline_id !=
+           last_n_latest_saved_snapshot_info_->request_id)) {
+    DVLOG(1) << " - Deleting previous last_n snapshot with offline_id "
+             << last_n_latest_saved_snapshot_info_->request_id;
     std::vector<int64_t> id{last_n_latest_saved_snapshot_info_->request_id};
     page_model_->DeletePagesByOfflineId(id, DeletePageCallback());
+    last_n_latest_saved_snapshot_info_.reset();
   }
 
   // Cancel any and all in flight snapshot tasks from the previous page.
   CancelInFlightSnapshots();
   downloads_snapshot_on_hold_ = false;
 
   // Always reset so that posted tasks get canceled.
   snapshot_controller_->Reset();
 
   // Check for conditions that should stop last_n from creating snapshots of
   // this page:
   // - It is an error page.
   // - The navigation is a POST as offline pages are never loaded for them.
   // - The navigated URL is not supported.
   // - The page being loaded is already an offline page.
   bool can_save =
       !navigation_handle->IsErrorPage() && !navigation_handle->IsPost() &&
       OfflinePageModel::CanSaveURL(web_contents()->GetLastCommittedURL()) &&
-      OfflinePageUtils::GetOfflinePageFromWebContents(web_contents()) ==
-          nullptr;
-  DVLOG_IF(1, !can_save) << " - Page can not be saved for offline usage";
+      current_offline_page == nullptr;
+  DVLOG_IF(1, !can_save)
+      << " - Page can not be saved for offline usage (reasons: "
+      << !navigation_handle->IsErrorPage() << ", "
+      << !navigation_handle->IsPost() << ", "
+      << OfflinePageModel::CanSaveURL(web_contents()->GetLastCommittedURL())
+      << ", " << (current_offline_page == nullptr) << ")";
 
   UMA_HISTOGRAM_BOOLEAN("OfflinePages.CanSaveRecentPage", can_save);
 
   if (!can_save)
     snapshot_controller_->Stop();
   last_n_listen_to_tab_hidden_ = can_save && !delegate_->IsLowEndDevice() &&
                                  IsOffliningRecentPagesEnabled();
   DVLOG_IF(1, can_save && !last_n_listen_to_tab_hidden_)
       << " - Page can not be saved by last_n";
 }
@@ skipping 53 matching lines @@
   last_n_ongoing_snapshot_info_ =
       base::MakeUnique<SnapshotProgressInfo>(GetRecentPagesClientId());
   DCHECK(last_n_ongoing_snapshot_info_->IsForLastN());
   DCHECK(snapshots_enabled_);
   // Remove previously captured pages for this tab.
   page_model_->GetOfflineIdsForClientId(
       GetRecentPagesClientId(),
       base::Bind(&RecentTabHelper::ContinueSnapshotWithIdsToPurge,
                  weak_ptr_factory_.GetWeakPtr(),
                  last_n_ongoing_snapshot_info_.get()));
+  last_n_latest_saved_snapshot_info_.reset();
 }
 
 void RecentTabHelper::WasShown() {
   // If the tab was closing and is now being shown, the closure was reverted.
   DVLOG_IF(0, tab_is_closing_) << "Tab is not closing anymore: "
                                << web_contents()->GetLastCommittedURL().spec();
   tab_is_closing_ = false;
 }
 
 void RecentTabHelper::WillCloseTab() {
@@ skipping 177 matching lines @@
 
 void RecentTabHelper::CancelInFlightSnapshots() {
   DVLOG_IF(1, last_n_ongoing_snapshot_info_)
       << " - Canceling ongoing last_n snapshot";
   DVLOG_IF(1, downloads_ongoing_snapshot_info_)
       << " - Canceling ongoing downloads snapshot";
   weak_ptr_factory_.InvalidateWeakPtrs();
   downloads_ongoing_snapshot_info_.reset();
   downloads_latest_saved_snapshot_info_.reset();
   last_n_ongoing_snapshot_info_.reset();
-  last_n_latest_saved_snapshot_info_.reset();
 }
 
 }  // namespace offline_pages