[NoStatePrefetch] Do not send responses to renderer in prefetch mode.

content/browser/loader/resource_dispatcher_host_impl.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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 1552 matching lines @@
       handler.reset(new AsyncResourceHandler(request, this));
     }
 
     // The RedirectToFileResourceHandler depends on being next in the chain.
     if (request_data.download_to_file) {
       handler.reset(
           new RedirectToFileResourceHandler(std::move(handler), request));
     }
   }
 
+  bool start_detached = request_data.download_to_network_cache_only;
+
   // Prefetches and <a ping> requests outlive their child process.
-  if (!sync_result && IsDetachableResourceType(request_data.resource_type)) {
-    handler.reset(new DetachableResourceHandler(
-        request,
-        base::TimeDelta::FromMilliseconds(kDefaultDetachableCancelDelayMs),
-        std::move(handler)));
+  if (!sync_result && (start_detached ||
+                       IsDetachableResourceType(request_data.resource_type))) {
+    std::unique_ptr<DetachableResourceHandler> detachable_handler =
+        base::MakeUnique<DetachableResourceHandler>(
+            request,
+            base::TimeDelta::FromMilliseconds(kDefaultDetachableCancelDelayMs),
+            std::move(handler));
+    if (start_detached)
+      detachable_handler->Detach();
+    handler = std::move(detachable_handler);
   }
 
   // PlzNavigate: If using --enable-browser-side-navigation, the
   // CrossSiteResourceHandler is not needed. This codepath is not used for the
   // actual navigation request, but only the subsequent blob URL load. This does
   // not require request transfers.
   if (!IsBrowserSideNavigationEnabled()) {
     // Install a CrossSiteResourceHandler for all main frame requests. This will
     // check whether a transfer is required and, if so, pause for the UI thread
     // to drive the transfer.
@@ skipping 1084 matching lines @@
         request_info->GetRouteID(), is_content_initiated, true, &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content