Last_n: Do not save a snapshot of a closing tab.

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 229 matching lines @@
   CancelInFlightSnapshots();
 }
 
 // TODO(carlosk): this method is also called when the tab is being closed, when
 // saving a snapshot is probably useless (low probability of the user undoing
 // the close). We should detect that and avoid the saving.
 void RecentTabHelper::WasHidden() {
   if (!IsOffliningRecentPagesEnabled())
     return;
 
-  // Return immediately if last_n is not listening to tab hidden events or if a
-  // last_n snapshot is currently being saved.
-  if (!last_n_listen_to_tab_hidden_ || last_n_ongoing_snapshot_info_)
+  // Return immediately if last_n is not listening to tab hidden events, if a
+  // last_n snapshot is currently being saved or if the tab is closing.
+  if (!last_n_listen_to_tab_hidden_ || last_n_ongoing_snapshot_info_ ||
+      tab_is_closing) {
+    DVLOG(1) << "Will not snapshot for last_n (reasons: "
+             << !last_n_listen_to_tab_hidden_ << ", "
+             << !!last_n_ongoing_snapshot_info_ << ", " << tab_is_closing
+             << ") for: " << web_contents()->GetLastCommittedURL().spec();
     return;
+  }
 
   // Do not save if page quality is too low.
   // Note: we assume page quality for a page can only increase.
   if (snapshot_controller_->current_page_quality() == PageQuality::POOR)
     return;
 
   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()));
 }
 
+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() {
+  DVLOG(1) << "Tab is now closing: "
+           << web_contents()->GetLastCommittedURL().spec();
+  tab_is_closing = true;
+}
+
 // TODO(carlosk): rename this to RequestSnapshot and make it return a bool
 // representing the acceptance of the snapshot request.
 void RecentTabHelper::StartSnapshot() {
   DCHECK_NE(PageQuality::POOR, snapshot_controller_->current_page_quality());
 
   // As long as snapshots are enabled for this tab, there are two situations
   // that allow for a navigation event to start a snapshot:
   // 1) There is a request on hold waiting for the page to be minimally loaded.
   if (snapshots_enabled_ && downloads_snapshot_on_hold_) {
     downloads_snapshot_on_hold_ = false;
@@ skipping 141 matching lines @@
 }
 
 void RecentTabHelper::CancelInFlightSnapshots() {
   weak_ptr_factory_.InvalidateWeakPtrs();
   downloads_ongoing_snapshot_info_.reset();
   downloads_latest_saved_snapshot_info_.reset();
   last_n_ongoing_snapshot_info_.reset();
 }
 
 }  // namespace offline_pages