Add histogram to measure the read deferral on crosswebsite navigation

content/browser/loader/resource_loader.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.
 
 #include "content/browser/loader/resource_loader.h"
 
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram.h"
 #include "base/time/time.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/loader/doomed_resource_handler.h"
 #include "content/browser/loader/resource_loader_delegate.h"
 #include "content/browser/loader/resource_request_info_impl.h"
 #include "content/browser/ssl/ssl_client_auth_handler.h"
 #include "content/browser/ssl/ssl_manager.h"
 #include "content/common/ssl_status_serialization.h"
 #include "content/public/browser/cert_store.h"
 #include "content/public/browser/resource_dispatcher_host_login_delegate.h"
@@ skipping 534 matching lines @@
            !request_->ssl_info().connection_status);
   }
 
   delegate_->DidReceiveResponse(this);
 
   bool defer = false;
   if (!handler_->OnResponseStarted(
           info->GetRequestID(), response.get(), &defer)) {
     Cancel();
   } else if (defer) {
+    read_deferral_start_time_ = base::TimeTicks::Now();
     deferred_stage_ = DEFERRED_READ;  // Read first chunk when resumed.
   }
 }
 
 void ResourceLoader::StartReading(bool is_continuation) {
   int bytes_read = 0;
   ReadMore(&bytes_read);
 
   // If IO is pending, wait for the URLRequest to call OnReadCompleted.
   if (request_->status().is_io_pending())
     return;
 
   if (!is_continuation || bytes_read <= 0) {
     OnReadCompleted(request_.get(), bytes_read);
   } else {
     // Else, trigger OnReadCompleted asynchronously to avoid starving the IO
     // thread in case the URLRequest can provide data synchronously.
     base::MessageLoop::current()->PostTask(
         FROM_HERE,
         base::Bind(&ResourceLoader::OnReadCompleted,
                    weak_ptr_factory_.GetWeakPtr(),
                    request_.get(),
                    bytes_read));
   }
 }
 
 void ResourceLoader::ResumeReading() {
   DCHECK(!is_deferred());
 
+  if (!read_deferral_start_time_.is_null()) {
+    UMA_HISTOGRAM_TIMES("Net.ResourceLoader.ReadDeferral",
+                        base::TimeTicks::Now() - read_deferral_start_time_);
+    read_deferral_start_time_ = base::TimeTicks();
+  }
   if (request_->status().is_success()) {
     StartReading(false);  // Read the next chunk (OK to complete synchronously).
   } else {
     ResponseCompleted();
   }
 }
 
 void ResourceLoader::ReadMore(int* bytes_read) {
   ResourceRequestInfoImpl* info = GetRequestInfo();
   DCHECK(!is_deferred());
@@ skipping 51 matching lines @@
     // we resume.
     deferred_stage_ = DEFERRED_FINISH;
   }
 }
 
 void ResourceLoader::CallDidFinishLoading() {
   delegate_->DidFinishLoading(this);
 }
 
 }  // namespace content