Experiment to disable Prerendering with fast wind-down

chrome/browser/prerender/prerender_manager.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 "chrome/browser/prerender/prerender_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <functional>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/single_thread_task_runner.h"
 #include "base/sys_info.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/timer/elapsed_timer.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/net/prediction_options.h"
 #include "chrome/browser/prerender/prerender_contents.h"
@@ skipping 844 matching lines @@
   // those prerenders is managed by the offliner.
   if (IsLowEndDevice() && origin != ORIGIN_OFFLINE)
     return nullptr;
 
   if ((origin == ORIGIN_LINK_REL_PRERENDER_CROSSDOMAIN ||
        origin == ORIGIN_LINK_REL_PRERENDER_SAMEDOMAIN) &&
       IsGoogleSearchResultURL(referrer.url)) {
     origin = ORIGIN_GWS_PRERENDER;
   }
 
+  if (IsPrerenderSilenceExperiment(origin))
+    return nullptr;
+
   GURL url = url_arg;
   GURL alias_url;
   if (IsControlGroup() && MaybeGetQueryStringBasedAliasURL(url, &alias_url))
     url = alias_url;
 
   // From here on, we will record a FinalStatus so we need to register with the
   // histogram tracking.
   histograms_->RecordPrerender(origin, url_arg);
 
   if (profile_->GetPrefs()->GetBoolean(prefs::kBlockThirdPartyCookies) &&
@@ skipping 338 matching lines @@
   if (!ActuallyPrerendering())
     return;
   int64_t recent_profile_bytes =
       profile_network_bytes_ - last_recorded_profile_network_bytes_;
   last_recorded_profile_network_bytes_ = profile_network_bytes_;
   DCHECK_GE(recent_profile_bytes, 0);
   histograms_->RecordNetworkBytes(
       origin, used, prerender_bytes, recent_profile_bytes);
 }
 
+bool PrerenderManager::IsPrerenderSilenceExperiment(Origin origin) const {
+  if (origin == ORIGIN_OFFLINE)
+    return false;
+
+  // The group name should contain expiration time formatted as:
+  //   "ExperimentYes_expires_YYYY-MM-DDTHH:MM:SSZ".
+  std::string group_name =
+      base::FieldTrialList::FindFullName("PrerenderSilence");
+  const char kExperimentPrefix[] = "ExperimentYes";
+  if (!base::StartsWith(group_name, kExperimentPrefix,
+                        base::CompareCase::INSENSITIVE_ASCII)) {
+    return false;
+  }
+  const char kExperimentPrefixWithExpiration[] = "ExperimentYes_expires_";
+  if (!base::StartsWith(group_name, kExperimentPrefixWithExpiration,
+                        base::CompareCase::INSENSITIVE_ASCII)) {
+    // Without expiration day in the group name, behave as a normal experiment,
+    // i.e. sticky to the Chrome session.
+    return true;
+  }
+  base::Time expiration_time;
+  if (!base::Time::FromString(
+          group_name.c_str() + (arraysize(kExperimentPrefixWithExpiration) - 1),
+          &expiration_time)) {
+    DLOG(ERROR) << "Could not parse expiration date in group: " << group_name;
+    return false;
+  }
+  return GetCurrentTime() < expiration_time;
+}
+
 NetworkPredictionStatus PrerenderManager::GetPredictionStatus() const {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   return CanPrefetchAndPrerenderUI(profile_->GetPrefs());
 }
 
 NetworkPredictionStatus PrerenderManager::GetPredictionStatusForOrigin(
     Origin origin) const {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   // <link rel=prerender> origins ignore the network state and the privacy
@@ skipping 54 matching lines @@
   DCHECK_EQ(1u, erased);
 }
 
 void PrerenderManager::SetPrerenderContentsFactoryForTest(
     PrerenderContents::Factory* prerender_contents_factory) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   prerender_contents_factory_.reset(prerender_contents_factory);
 }
 
 }  // namespace prerender