Check WebContentsObservers before showing Previews InfoBars

chrome/browser/previews/previews_infobar_delegate.cc

Index: chrome/browser/previews/previews_infobar_delegate.cc
diff --git a/chrome/browser/previews/previews_infobar_delegate.cc b/chrome/browser/previews/previews_infobar_delegate.cc
index 3a34ccddb693d3f087eb995260c839f582692a79..987b4a0a4408d5b5e672ed30bb39e77eb8ff1fad 100644
--- a/chrome/browser/previews/previews_infobar_delegate.cc
+++ b/chrome/browser/previews/previews_infobar_delegate.cc
@@ -59,12 +59,16 @@ void PreviewsInfoBarDelegate::Create(
     const OnDismissPreviewsInfobarCallback& on_dismiss_callback) {
   PreviewsInfoBarTabHelper* infobar_tab_helper =
       PreviewsInfoBarTabHelper::FromWebContents(web_contents);
-  if (infobar_tab_helper->displayed_preview_infobar())
-    return;
-
   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;
+
   infobars::InfoBar* infobar =
       infobar_service->AddInfoBar(infobar_service->CreateConfirmInfoBar(
           std::unique_ptr<ConfirmInfoBarDelegate>(new PreviewsInfoBarDelegate(