Fix crash when using remote DevTools on CrOS WebUI - check for response_headers

BUG=385677

Review URL: https://codereview.chromium.org/332393004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@277890 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

@@ -662,7 +662,7 @@ void ChromeResourceDispatcherHostDelegate::OnResponseStarted(
   if (request_spec == chrome::kChromeUIChromeSigninURL) {
 #endif
     net::HttpResponseHeaders* response_headers = request->response_headers();
-    if (response_headers->HasHeader("x-frame-options"))
+    if (response_headers && response_headers->HasHeader("x-frame-options"))
       response_headers->RemoveHeader("x-frame-options");
   }