Add test to check for crash caused by stale WebContents in chrome://interstitials

chrome/browser/ui/webui/interstitials/interstitial_ui.cc

 // Copyright 2014 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/ui/webui/interstitials/interstitial_ui.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
@@ skipping 325 matching lines @@
 
 std::string InterstitialHTMLSource::GetContentSecurityPolicyImgSrc() const {
   return "img-src data:;";
 }
 
 void InterstitialHTMLSource::StartDataRequest(
     const std::string& path,
     const content::ResourceRequestInfo::WebContentsGetter& wc_getter,
     const content::URLDataSource::GotDataCallback& callback) {
   content::WebContents* web_contents = wc_getter.Run();
+  if (!web_contents) {
+    // When browser-side navigation is enabled, web_contents can be null if
+    // the tab is closing. Nothing to do in this case.
+    return;
+  }
   std::unique_ptr<content::InterstitialPageDelegate> interstitial_delegate;
   if (base::StartsWith(path, "ssl", base::CompareCase::SENSITIVE)) {
     interstitial_delegate.reset(CreateSSLBlockingPage(web_contents));
   } else if (base::StartsWith(path, "safebrowsing",
                               base::CompareCase::SENSITIVE)) {
     interstitial_delegate.reset(CreateSafeBrowsingBlockingPage(web_contents));
   } else if (base::StartsWith(path, "clock", base::CompareCase::SENSITIVE)) {
     interstitial_delegate.reset(CreateBadClockBlockingPage(web_contents));
   }
 #if BUILDFLAG(ENABLE_CAPTIVE_PORTAL_DETECTION)
   else if (base::StartsWith(path, "captiveportal",
                             base::CompareCase::SENSITIVE))
   {
     interstitial_delegate.reset(CreateCaptivePortalBlockingPage(web_contents));
   }
 #endif
   std::string html;
   if (interstitial_delegate.get()) {
     html = interstitial_delegate.get()->GetHTMLContents();
   } else {
     html = ResourceBundle::GetSharedInstance()
                           .GetRawDataResource(IDR_SECURITY_INTERSTITIAL_UI_HTML)
                           .as_string();
   }
   scoped_refptr<base::RefCountedString> html_bytes = new base::RefCountedString;
   html_bytes->data().assign(html.begin(), html.end());
   callback.Run(html_bytes.get());
 }