Cleanup by removing thread hop resource throttle code; experiment's over.

BUG=572740
R=davidben@chromium.org

Review-Url: https://codereview.chromium.org/2282523002
Cr-Commit-Position: refs/heads/master@{#414729}

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

@@ -34,7 +34,6 @@
 #include "chrome/browser/renderer_host/chrome_navigation_data.h"
 #include "chrome/browser/renderer_host/predictor_resource_throttle.h"
 #include "chrome/browser/renderer_host/safe_browsing_resource_throttle.h"
-#include "chrome/browser/renderer_host/thread_hop_resource_throttle.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
 #include "chrome/browser/search/search.h"
 #include "chrome/browser/search_engines/template_url_service_factory.h"
@@ -638,9 +637,6 @@ void ChromeResourceDispatcherHostDelegate::AppendStandardResourceThrottles(
     throttles->push_back(new prerender::PrerenderResourceThrottle(request));
   }
 
-  if (ThreadHopResourceThrottle::IsEnabled())
-    throttles->push_back(new ThreadHopResourceThrottle);
-
   std::unique_ptr<PredictorResourceThrottle> predictor_throttle =
       PredictorResourceThrottle::MaybeCreate(request, io_data);
   if (predictor_throttle)

chrome/browser/renderer_host/thread_hop_resource_throttle.cc

-// Copyright 2015 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/renderer_host/thread_hop_resource_throttle.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/location.h"
-#include "base/metrics/field_trial.h"
-#include "base/metrics/histogram_macros.h"
-#include "base/strings/string_util.h"
-#include "base/time/time.h"
-#include "content/public/browser/browser_thread.h"
-#include "content/public/browser/resource_controller.h"
-
-ThreadHopResourceThrottle::ThreadHopResourceThrottle() : weak_factory_(this) {}
-
-ThreadHopResourceThrottle::~ThreadHopResourceThrottle() {}
-
-bool ThreadHopResourceThrottle::IsEnabled() {
-  const std::string group_name =
-      base::FieldTrialList::FindFullName("ThreadHopResourceThrottle");
-  return base::StartsWith(group_name, "Enabled", base::CompareCase::SENSITIVE);
-}
-
-void ThreadHopResourceThrottle::WillStartRequest(bool* defer) {
-  *defer = true;
-  ResumeAfterThreadHop();
-}
-
-void ThreadHopResourceThrottle::WillRedirectRequest(
-    const net::RedirectInfo& redirect_info,
-    bool* defer) {
-  *defer = true;
-  ResumeAfterThreadHop();
-}
-
-void ThreadHopResourceThrottle::WillProcessResponse(bool* defer) {
-  *defer = true;
-  ResumeAfterThreadHop();
-}
-
-const char* ThreadHopResourceThrottle::GetNameForLogging() const {
-  return "ThreadHopResourceThrottle";
-}
-
-void ThreadHopResourceThrottle::ResumeAfterThreadHop() {
-  content::BrowserThread::PostTaskAndReply(
-      content::BrowserThread::UI, FROM_HERE, base::Bind(&base::DoNothing),
-      base::Bind(&ThreadHopResourceThrottle::Resume, weak_factory_.GetWeakPtr(),
-                 base::TimeTicks::Now()));
-}
-
-void ThreadHopResourceThrottle::Resume(const base::TimeTicks& time) {
-  UMA_HISTOGRAM_TIMES("Net.ThreadHopResourceThrottleTime",
-                      base::TimeTicks::Now() - time);
-  controller()->Resume();
-}

chrome/browser/renderer_host/thread_hop_resource_throttle.h

-// Copyright 2015 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.
-
-#ifndef CHROME_BROWSER_RENDERER_HOST_THREAD_HOP_RESOURCE_THROTTLE_H_
-#define CHROME_BROWSER_RENDERER_HOST_THREAD_HOP_RESOURCE_THROTTLE_H_
-
-#include "base/macros.h"
-#include "base/memory/weak_ptr.h"
-#include "content/public/browser/resource_throttle.h"
-
-namespace base {
-class TimeTicks;
-}
-
-// A ResourceThrottle which defers request start, redirect, and response
-// completion on an IO to UI to IO round-trip. This throttle will be added on a
-// field trial to determine the cost of making some resource-related decisions
-// on the UI thread. See https://crbug.com/524228.
-class ThreadHopResourceThrottle : public content::ResourceThrottle {
- public:
-  ThreadHopResourceThrottle();
-  ~ThreadHopResourceThrottle() override;
-
-  static bool IsEnabled();
-
-  // content::ResourceThrottle:
-  void WillStartRequest(bool* defer) override;
-  void WillRedirectRequest(const net::RedirectInfo& redirect_info,
-                           bool* defer) override;
-  void WillProcessResponse(bool* defer) override;
-  const char* GetNameForLogging() const override;
-
- private:
-  void ResumeAfterThreadHop();
-  void Resume(const base::TimeTicks& time);
-
-  base::WeakPtrFactory<ThreadHopResourceThrottle> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(ThreadHopResourceThrottle);
-};
-
-#endif  // CHROME_BROWSER_RENDERER_HOST_THREAD_HOP_RESOURCE_THROTTLE_H_

chrome/chrome_browser.gypi

@@ -541,8 +541,6 @@
       'browser/renderer_host/chrome_resource_dispatcher_host_delegate.h',
       'browser/renderer_host/predictor_resource_throttle.cc',
       'browser/renderer_host/predictor_resource_throttle.h',
-      'browser/renderer_host/thread_hop_resource_throttle.cc',
-      'browser/renderer_host/thread_hop_resource_throttle.h',
       'browser/renderer_preferences_util.cc',
       'browser/renderer_preferences_util.h',
       'browser/resource_delegate_mac.h',

tools/metrics/histograms/histograms.xml

@@ -32752,6 +32752,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Net.ThreadHopResourceThrottleTime" units="ms">
   <owner>davidben@chromium.org</owner>
+  <obsolete>
+    Experiment complete, code removed.
+  </obsolete>
   <summary>
     The time it took to do an IO to UI round-trip in the
     ThreadHopResourceThrottle. This is part of an experiment to determine the