PlzNavigate: improve bf navigations metrics

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 2222 matching lines @@
     std::unique_ptr<net::URLRequest> request,
     std::unique_ptr<ResourceHandler> handler) {
   DCHECK(!request->is_pending());
   ResourceRequestInfoImpl* info =
       ResourceRequestInfoImpl::ForRequest(request.get());
 
   // Log metrics for back-forward navigations.
   // TODO(clamy): Remove this once we understand the reason behind the
   // back-forward PLT regression with PlzNavigate
   if ((info->GetPageTransition() & ui::PAGE_TRANSITION_FORWARD_BACK) &&
-      IsResourceTypeFrame(info->GetResourceType())) {
+      IsResourceTypeFrame(info->GetResourceType()) &&
+      !request->url().SchemeIsBlob()) {

[nasko, 2017/06/19 18:16:55]

Maybe we can log these only for http/https cases, since other schemes are
unlikely to hit the network. I also think the page load metrics code only
considers http/https, so it will be more consistent with those?

If you end up changing this one, then it will be good to keep it in sync with
the other histogram added in resource_loader.cc.

[clamy, 2017/06/20 15:14:35]

Done.

     LogBackForwardNavigationFlagsHistogram(request->load_flags());
   }
 
   if ((TimeTicks::Now() - last_user_gesture_time_) <
       TimeDelta::FromMilliseconds(kUserGestureWindowMs)) {
     request->SetLoadFlags(request->load_flags() | net::LOAD_MAYBE_USER_GESTURE);
   }
 
   // Add the memory estimate that starting this request will consume.
   info->set_memory_cost(CalculateApproximateMemoryCost(request.get()));
@@ skipping 446 matching lines @@
                                  &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content