New Tab Page: chrome-search://local-ntp/ files should not be cachable

chrome/browser/search/local_ntp_source.cc

 // Copyright 2013 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/search/local_ntp_source.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 232 matching lines @@
 std::string LocalNtpSource::GetMimeType(
     const std::string& path) const {
   const std::string stripped_path = StripParameters(path);
   for (size_t i = 0; i < arraysize(kResources); ++i) {
     if (stripped_path == kResources[i].filename)
       return kResources[i].mime_type;
   }
   return std::string();
 }
 
+bool LocalNtpSource::AllowCaching() const {
+  // Some resources served by LocalNtpSource, i.e. config.js, are dynamically
+  // generated and could differ on each access. To avoid using old cached
+  // content on reload, disallow caching here. Otherwise, it fails to reflect
+  // newly revised user configurations in the page.
+  return false;
+}
+
 bool LocalNtpSource::ShouldServiceRequest(
     const net::URLRequest* request) const {
   DCHECK(request->url().host_piece() == chrome::kChromeSearchLocalNtpHost);
   if (!InstantIOContext::ShouldServiceRequest(request))
     return false;
 
   if (request->url().SchemeIs(chrome::kChromeSearchScheme)) {
     std::string filename;
     webui::ParsePathAndScale(request->url(), &filename, NULL);
     for (size_t i = 0; i < arraysize(kResources); ++i) {
       if (filename == kResources[i].filename)
         return true;
     }
   }
   return false;
 }
 
 std::string LocalNtpSource::GetContentSecurityPolicyChildSrc() const {
   // Allow embedding of most visited iframes.
   return base::StringPrintf("child-src %s;",
                             chrome::kChromeSearchMostVisitedUrl);
 }