Making offline previews freshness configurable

components/previews/core/previews_experiments.cc

 // Copyright 2016 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 "components/previews/core/previews_experiments.h"
 
 #include <map>
 #include <string>
 
 #include "base/logging.h"
@@ skipping 41 matching lines @@
     "per_host_black_list_duration_in_days";
 
 // The amount of time a host remains blacklisted due to opt outs.
 const char kHostIndifferentBlackListDurationInDays[] =
     "host_indifferent_black_list_duration_in_days";
 
 // The amount of time after any opt out that no previews should be shown.
 const char kSingleOptOutDurationInSeconds[] =
     "single_opt_out_duration_in_seconds";
 
+// The amount of time that an offline page is considered fresh enough to be
+// shown as a preview.
+const char kOfflinePreviewFreshnessDurationInDays[] =
+    "offline_preview_freshness_duration_in_days";
+
 // The string that corresponds to enabled for the variation param experiments.
 const char kExperimentEnabled[] = "true";
 
 // Returns the parameter value of |param| as a string. If there is no value for
 // |param|, returns an empty string.
 std::string ParamValue(const std::string& param) {
   if (!IsIncludedInClientSidePreviewsExperimentsFieldTrial())
     return std::string();
   std::map<std::string, std::string> experiment_params;
   if (!variations::GetVariationParams(kClientSidePreviewsFieldTrial,
@@ skipping 74 matching lines @@
 
 base::TimeDelta SingleOptOutDuration() {
   std::string param_value = ParamValue(kSingleOptOutDurationInSeconds);
   int duration;
   if (!base::StringToInt(param_value, &duration)) {
     return base::TimeDelta::FromSeconds(60 * 5);
   }
   return base::TimeDelta::FromSeconds(duration);
 }
 
+base::TimeDelta OfflinePreviewFreshnessDuration() {
+  std::string param_value = ParamValue(kOfflinePreviewFreshnessDurationInDays);
+  int duration;
+  if (!base::StringToInt(param_value, &duration)) {
+    return base::TimeDelta::FromDays(7);
+  }
+  return base::TimeDelta::FromDays(duration);
+}
+
 }  // namespace params
 
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial() {
   // By convention, an experiment in the client-side previews study enables use
   // of at least one client-side previews optimization if its name begins with
   // "Enabled."
   return base::StartsWith(
       base::FieldTrialList::FindFullName(kClientSidePreviewsFieldTrial),
       kEnabled, base::CompareCase::SENSITIVE);
 }
@@ skipping 11 matching lines @@
 bool EnableOfflinePreviewsForTesting() {
   std::map<std::string, std::string> params;
   params[kOfflinePagesSlowNetwork] = kExperimentEnabled;
   return variations::AssociateVariationParams(kClientSidePreviewsFieldTrial,
                                               kEnabled, params) &&
          base::FieldTrialList::CreateFieldTrial(kClientSidePreviewsFieldTrial,
                                                 kEnabled);
 }
 
 }  // namespace previews