Use WeakPtr when loading offline page

Bug: 1111307
Change-Id: Ied4969e60772cf0574cd22c02c0e6688fd89acba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332438
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793596}

ios/chrome/browser/reading_list/offline_page_tab_helper.h

@@ -134,6 +134,11 @@ class OfflinePageTabHelper : public web::WebStateUserData<OfflinePageTabHelper>,
   bool navigation_is_renderer_initiated_ = false;
 
   WEB_STATE_USER_DATA_KEY_DECL();
+
+  // Member variables should appear before the WeakPtrFactory, to ensure
+  // that any WeakPtrs to OfflinePageTabHelper are invalidated before its
+  // members variable's destructors are executed, rendering them invalid.
+  base::WeakPtrFactory<OfflinePageTabHelper> weak_factory_{this};
 };
 
 #endif  // IOS_CHROME_BROWSER_READING_LIST_OFFLINE_PAGE_TAB_HELPER_H_

ios/chrome/browser/reading_list/offline_page_tab_helper.mm

@@ -289,9 +289,9 @@ void OfflinePageTabHelper::PresentOfflinePageForOnlineUrl(const GURL& url) {
       {base::MayBlock(), base::TaskPriority::USER_BLOCKING,
        base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
       base::BindOnce(&GetOfflineData, offline_root, offline_path),
-      base::BindOnce(&OfflinePageTabHelper::LoadData, base::Unretained(this),
-                     last_navigation_started_, entry_url,
-                     offline_path.Extension()));
+      base::BindOnce(&OfflinePageTabHelper::LoadData,
+                     weak_factory_.GetWeakPtr(), last_navigation_started_,
+                     entry_url, offline_path.Extension()));
 }
 
 bool OfflinePageTabHelper::HasDistilledVersionForOnlineUrl(