[Reading List] Check web state after the distillation delay.

ios/chrome/browser/reading_list/reading_list_distiller_page.mm

 // 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 "ios/chrome/browser/reading_list/reading_list_distiller_page.h"
 
 #include "base/bind.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 35 matching lines @@
 ReadingListDistillerPageDelegate::ReadingListDistillerPageDelegate() {}
 ReadingListDistillerPageDelegate::~ReadingListDistillerPageDelegate() {}
 
 ReadingListDistillerPage::ReadingListDistillerPage(
     web::BrowserState* browser_state,
     FaviconWebStateDispatcher* web_state_dispatcher,
     ReadingListDistillerPageDelegate* delegate)
     : dom_distiller::DistillerPageIOS(browser_state),
       web_state_dispatcher_(web_state_dispatcher),
       delegate_(delegate),
+      delayed_task_id_(0),
       weak_ptr_factory_(this) {
   DCHECK(delegate);
 }
 
 ReadingListDistillerPage::~ReadingListDistillerPage() {}
 
 void ReadingListDistillerPage::DistillPageImpl(const GURL& url,
                                                const std::string& script) {
   std::unique_ptr<web::WebState> old_web_state = DetachWebState();
   if (old_web_state) {
     web_state_dispatcher_->ReturnWebState(std::move(old_web_state));
   }
   std::unique_ptr<web::WebState> new_web_state =
       web_state_dispatcher_->RequestWebState();
   AttachWebState(std::move(new_web_state));
   original_url_ = url;
+  delayed_task_id_++;
   FetchFavicon(url);
 
   DistillerPageIOS::DistillPageImpl(url, script);
 
   // WKWebView sets the document.hidden property to true and the
   // document.visibilityState to prerender if the page is not added to a view
   // hierarchy. Some pages may not render their content in these conditions.
   // Add the view and move it out of the screen far in the top left corner of
   // the coordinate space.
   CGRect frame = [[[UIApplication sharedApplication] keyWindow] frame];
@@ skipping 16 matching lines @@
   favicon_driver->FetchFavicon(page_url);
 }
 
 void ReadingListDistillerPage::OnDistillationDone(const GURL& page_url,
                                                   const base::Value* value) {
   std::unique_ptr<web::WebState> old_web_state = DetachWebState();
   if (old_web_state) {
     [old_web_state->GetView() removeFromSuperview];
     web_state_dispatcher_->ReturnWebState(std::move(old_web_state));
   }
+  delayed_task_id_++;
   DistillerPageIOS::OnDistillationDone(page_url, value);
 }
 
 bool ReadingListDistillerPage::IsLoadingSuccess(
     web::PageLoadCompletionStatus load_completion_status) {
   if (load_completion_status != web::PageLoadCompletionStatus::SUCCESS) {
     return false;
   }
   if (!CurrentWebState() || !CurrentWebState()->GetNavigationManager() ||
       !CurrentWebState()->GetNavigationManager()->GetLastCommittedItem()) {
@@ skipping 33 matching lines @@
     DistillerPageIOS::OnLoadURLDone(load_completion_status);
     return;
   }
   FetchFavicon(CurrentWebState()->GetVisibleURL());
 
   // Page is loaded but rendering may not be done yet. Give a delay to the page.
   base::WeakPtr<ReadingListDistillerPage> weak_this =
       weak_ptr_factory_.GetWeakPtr();
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE,
-      base::Bind(&ReadingListDistillerPage::DelayedOnLoadURLDone, weak_this),
+      base::Bind(&ReadingListDistillerPage::DelayedOnLoadURLDone, weak_this,
+                 delayed_task_id_),
       base::TimeDelta::FromSeconds(kPageLoadDelayInSeconds));
 }
 
-void ReadingListDistillerPage::DelayedOnLoadURLDone() {
+void ReadingListDistillerPage::DelayedOnLoadURLDone(int delayed_task_id) {
+  if (!CurrentWebState() || delayed_task_id != delayed_task_id_) {
+    // Something interrupted the distillation.
+    // Abort here.
+    return;
+  }
   if (IsGoogleCachedAMPPage()) {
     // Workaround for Google AMP pages.
     HandleGoogleCachedAMPPage();
   } else {
     ContinuePageDistillation();
   }
 }
 
 void ReadingListDistillerPage::ContinuePageDistillation() {
   // The page is ready to be distilled.
@@ skipping 66 matching lines @@
   if (!new_gurl.is_valid()) {
     return false;
   }
   FetchFavicon(new_gurl);
   web::NavigationManager::WebLoadParams params(new_gurl);
   CurrentWebState()->GetNavigationManager()->LoadURLWithParams(params);
   return true;
 }
 
 }  // namespace reading_list