Add a UMA histogram for measuring DetachableResourceHandler duration

content/browser/loader/detachable_resource_handler.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 "content/browser/loader/detachable_resource_handler.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "content/browser/loader/null_resource_controller.h"
 #include "content/browser/loader/resource_controller.h"
 #include "content/browser/loader/resource_request_info_impl.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_status.h"
 
 namespace {
@@ skipping 212 matching lines @@
   }
 
   HoldController(std::move(controller));
   next_handler_->OnReadCompleted(bytes_read,
                                  base::MakeUnique<Controller>(this));
 }
 
 void DetachableResourceHandler::OnResponseCompleted(
     const net::URLRequestStatus& status,
     std::unique_ptr<ResourceController> controller) {
+  UMA_HISTOGRAM_MEDIUM_TIMES(
+      "Net.DetachableResourceHandler.Duration",
+      base::TimeTicks::Now() - request()->creation_time());
+
   // No DCHECK(!is_deferred_) as the request may have been cancelled while
   // deferred.
 
   if (!next_handler_) {
     controller->Resume();
     return;
   }
 
   is_finished_ = true;
 
@@ skipping 18 matching lines @@
 void DetachableResourceHandler::OnTimedOut() {
   // Requests are only timed out after being detached, and shouldn't be deferred
   // once detached.
   DCHECK(!next_handler_);
   DCHECK(!has_controller());
 
   OutOfBandCancel(net::ERR_ABORTED, true /* tell_renderer */);
 }
 
 }  // namespace content