Fix devtools unable to start a shared workers.

chrome/browser/ui/webui/ntp/new_tab_ui.cc

 // Copyright (c) 2012 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/ntp/new_tab_ui.h"
 
 #include <memory>
 
 #include "base/i18n/rtl.h"
 #include "base/memory/ref_counted_memory.h"
@@ skipping 187 matching lines @@
   }
 
   if (!path.empty() && path[0] != '#') {
     // A path under new-tab was requested; it's likely a bad relative
     // URL from the new tab page, but in any case it's an error.
     NOTREACHED() << path << " should not have been requested on the NTP";
     callback.Run(NULL);
     return;
   }
 
+  content::WebContents* web_contents = wc_getter.Run();
   content::RenderProcessHost* render_host =
-      wc_getter.Run()->GetRenderProcessHost();
+      web_contents ? web_contents->GetRenderProcessHost() : nullptr;
   NTPResourceCache::WindowType win_type = NTPResourceCache::GetWindowType(
       profile_, render_host);
   scoped_refptr<base::RefCountedMemory> html_bytes(
       NTPResourceCacheFactory::GetForProfile(profile_)->
       GetNewTabHTML(win_type));
 
   callback.Run(html_bytes.get());
 }
 
 std::string NewTabUI::NewTabHTMLSource::GetMimeType(const std::string& resource)
@@ skipping 35 matching lines @@
 void NewTabUI::NewTabHTMLSource::AddResource(const char* resource,
                                              const char* mime_type,
                                              int resource_id) {
   DCHECK(resource);
   DCHECK(mime_type);
   resource_map_[std::string(resource)] =
       std::make_pair(std::string(mime_type), resource_id);
 }
 
 NewTabUI::NewTabHTMLSource::~NewTabHTMLSource() {}