Check WebContentsObservers before showing Previews InfoBars

chrome/browser/previews/previews_infobar_delegate.cc

 // 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 "chrome/browser/previews/previews_infobar_delegate.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "chrome/browser/android/android_theme_resources.h"
 #include "chrome/browser/infobars/infobar_service.h"
 #include "chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.h"
@@ skipping 41 matching lines @@
 }
 
 // static
 void PreviewsInfoBarDelegate::Create(
     content::WebContents* web_contents,
     PreviewsInfoBarType infobar_type,
     bool is_data_saver_user,
     const OnDismissPreviewsInfobarCallback& on_dismiss_callback) {
   PreviewsInfoBarTabHelper* infobar_tab_helper =
       PreviewsInfoBarTabHelper::FromWebContents(web_contents);
+  InfoBarService* infobar_service =
+      InfoBarService::FromWebContents(web_contents);
+
+  // The WebContents may not have TabHelpers set. If TabHelpers are not set,
+  // don't show Previews infobars.
+  if (!infobar_tab_helper || !infobar_service)
+    return;
   if (infobar_tab_helper->displayed_preview_infobar())
     return;
 
-  InfoBarService* infobar_service =
-      InfoBarService::FromWebContents(web_contents);
-
   infobars::InfoBar* infobar =
       infobar_service->AddInfoBar(infobar_service->CreateConfirmInfoBar(
           std::unique_ptr<ConfirmInfoBarDelegate>(new PreviewsInfoBarDelegate(
               web_contents, infobar_type, is_data_saver_user,
               on_dismiss_callback))));
 
   if (infobar && (infobar_type == LITE_PAGE || infobar_type == LOFI)) {
     auto* data_reduction_proxy_settings =
         DataReductionProxyChromeSettingsFactory::GetForBrowserContext(
             web_contents->GetBrowserContext());
@@ skipping 71 matching lines @@
     auto* data_reduction_proxy_settings =
         DataReductionProxyChromeSettingsFactory::GetForBrowserContext(
             web_contents->GetBrowserContext());
     data_reduction_proxy_settings->IncrementLoFiUserRequestsForImages();
   } else if (infobar_type_ == OFFLINE) {
     web_contents->GetController().Reload(content::ReloadType::NORMAL, true);
   }
 
   return true;
 }