Remove overeager DCHECK in SnapshotController.

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 47 matching lines @@
   // WebContents with its origin as well.
   never_do_snapshots_ = web_contents->GetBrowserContext()->IsOffTheRecord();
 }
 
 RecentTabHelper::~RecentTabHelper() {
 }
 
 void RecentTabHelper::DidFinishNavigation(
     content::NavigationHandle* navigation_handle) {
   if (navigation_handle->IsInMainFrame() &&
-      navigation_handle->HasCommitted() &&
-      !navigation_handle->IsErrorPage()) {
+      navigation_handle->HasCommitted()) {
+    // Cancel tasks in flight that relate to the previous page.
+    weak_ptr_factory_.InvalidateWeakPtrs();
     // New navigation, new snapshot session.
     snapshot_controller_->Reset();
     snapshot_url_ = GURL::EmptyGURL();
   }
 }
 
 void RecentTabHelper::DocumentAvailableInMainFrame() {
   snapshot_controller_->DocumentAvailableInMainFrame();
 }
 
@@ skipping 121 matching lines @@
     std::unique_ptr<TestArchiveFactory> test_archive_factory) {
   test_archive_factory_ = std::move(test_archive_factory);
 }
 
 void RecentTabHelper::SetTaskRunnerForTest(
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
   snapshot_controller_.reset(new SnapshotController(task_runner, this));
 }
 
 }  // namespace offline_pages