[Cleanup] Remove the obsolete Prerender field trial.

chrome/browser/prerender/prerender_field_trial.cc

Index: chrome/browser/prerender/prerender_field_trial.cc
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index 6e3dea425c5594e9f2d8d0b4197a2987df9ec37b..54d3c3801cec1c567d686fc035122ee450a3bc5c 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -6,11 +6,6 @@
 
 #include "base/command_line.h"
 #include "base/logging.h"
-#include "base/metrics/field_trial.h"
-#include "base/metrics/histogram.h"
-#include "base/prefs/pref_service.h"
-#include "base/strings/string_number_conversions.h"
-#include "base/strings/string_split.h"
 #include "chrome/browser/net/prediction_options.h"
 #include "chrome/browser/predictors/autocomplete_action_predictor.h"
 #include "chrome/browser/prerender/prerender_manager.h"
@@ -18,224 +13,43 @@
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/common/chrome_switches.h"
-#include "chrome/common/chrome_version_info.h"
-#include "components/metrics/metrics_service.h"
-#include "components/variations/variations_associated_data.h"
 
-using base::FieldTrial;
-using base::FieldTrialList;
-using base::StringToInt;
 using std::string;
-using std::vector;
 
 namespace prerender {
 
 namespace {
 
-const char kDisabledGroup[] = "Disabled";
-const char kEnabledGroup[] = "Enabled";
-
-const char kLocalPredictorSpecTrialName[] = "PrerenderLocalPredictorSpec";
-const char kLocalPredictorKeyName[] = "LocalPredictor";
-const char kLocalPredictorUnencryptedSyncOnlyKeyName[] =
-    "LocalPredictorUnencryptedSyncOnly";
-const char kLocalPredictorNetworkPredictionEnabledOnly[] =
-    "LocalPredictorNetworkPredictionEnabledOnly";
-const char kLocalPredictorOnCellularOnly[] = "LocalPredictorOnCellularOnly";
-const char kSideEffectFreeWhitelistKeyName[] = "SideEffectFreeWhitelist";
-const char kPrerenderLaunchKeyName[] = "PrerenderLaunch";
-const char kPrerenderAlwaysControlKeyName[] = "PrerenderAlwaysControl";
-const char kPrerenderPrefetchKeyName[] = "PrerenderPrefetch";
-const char kPrerenderQueryPrerenderServiceKeyName[] =
-    "PrerenderQueryPrerenderService";
-const char kPrerenderQueryPrerenderServiceCurrentURLKeyName[] =
-    "PrerenderQueryPrerenderServiceCurrentURL";
-const char kPrerenderQueryPrerenderServiceCandidateURLsKeyName[] =
-    "PrerenderQueryPrerenderServiceCandidateURLs";
-const char kPrerenderServiceBehaviorIDKeyName[] = "PrerenderServiceBehaviorID";
-const char kPrerenderServiceFetchTimeoutKeyName[] =
-    "PrerenderServiceFetchTimeoutMs";
-const char kPrefetchListTimeoutKeyName[] = "PrefetchListTimeoutSeconds";
-const char kPrerenderTTLKeyName[] = "PrerenderTTLSeconds";
-const char kPrerenderPriorityHalfLifeTimeKeyName[] =
-    "PrerenderPriorityHalfLifeTimeSeconds";
-const char kMaxConcurrentPrerenderKeyName[] = "MaxConcurrentPrerenders";
-const char kMaxLaunchPrerenderKeyName[] = "MaxLaunchPrerenders";
-const char kSkipFragment[] = "SkipFragment";
-const char kSkipHTTPS[] = "SkipHTTPS";
-const char kSkipWhitelist[] = "SkipWhitelist";
-const char kSkipServiceWhitelist[] = "SkipServiceWhitelist";
-const char kSkipLoggedIn[] = "SkipLoggedIn";
-const char kSkipDefaultNoPrerender[] = "SkipDefaultNoPrerender";
-const char kPrerenderServiceURLPrefixParameterName[] =
-    "PrerenderServiceURLPrefix";
 const char kDefaultPrerenderServiceURLPrefix[] =
     "https://clients4.google.com/prerenderservice/?q=";
-const int kMinPrerenderServiceTimeoutMs = 1;
-const int kMaxPrerenderServiceTimeoutMs = 10000;
 const int kDefaultPrerenderServiceTimeoutMs = 1000;
-const int kMinPrefetchListTimeoutSeconds = 1;
-const int kMaxPrefetchListTimeoutSeconds = 1800;
 const int kDefaultPrefetchListTimeoutSeconds = 300;
-const char kSkipPrerenderLocalCanadidates[] = "SkipPrerenderLocalCandidates";
-const char kSkipPrerenderServiceCanadidates[] =
-    "SkipPrerenderServiceCandidates";
-
-void SetupPrerenderFieldTrial() {
-  const FieldTrial::Probability divisor = 1000;
-
-  FieldTrial::Probability control_probability;
-  FieldTrial::Probability experiment_multi_prerender_probability;
-  FieldTrial::Probability experiment_15min_ttl_probability;
-  FieldTrial::Probability experiment_no_use_probability;
-  FieldTrial::Probability experiment_match_complete_probability;
-
-  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
-  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
-      channel == chrome::VersionInfo::CHANNEL_BETA) {
-    // Use very conservatives and stable settings in beta and stable.
-    const FieldTrial::Probability release_prerender_enabled_probability = 970;
-    const FieldTrial::Probability release_control_probability = 10;
-    const FieldTrial::Probability
-        release_experiment_multi_prerender_probability = 0;
-    const FieldTrial::Probability release_experiment_15min_ttl_probability = 10;
-    const FieldTrial::Probability release_experiment_no_use_probability = 0;
-    const FieldTrial::Probability
-        release_experiment_match_complete_probability = 10;
-    static_assert(
-        release_prerender_enabled_probability +
-        release_control_probability +
-        release_experiment_multi_prerender_probability +
-        release_experiment_15min_ttl_probability +
-        release_experiment_no_use_probability +
-        release_experiment_match_complete_probability == divisor,
-        "release experiment probabilities must equal divisor");
-
-    control_probability = release_control_probability;
-    experiment_multi_prerender_probability =
-        release_experiment_multi_prerender_probability;
-    experiment_15min_ttl_probability = release_experiment_15min_ttl_probability;
-    experiment_no_use_probability = release_experiment_no_use_probability;
-    experiment_match_complete_probability =
-        release_experiment_match_complete_probability;
-  } else {
-    // In testing channels, use more experiments and a larger control group to
-    // improve quality of data.
-    const FieldTrial::Probability dev_prerender_enabled_probability = 200;
-    const FieldTrial::Probability dev_control_probability = 200;
-    const FieldTrial::Probability
-        dev_experiment_multi_prerender_probability = 200;
-    const FieldTrial::Probability dev_experiment_15min_ttl_probability = 100;
-    const FieldTrial::Probability dev_experiment_no_use_probability = 100;
-    const FieldTrial::Probability
-        dev_experiment_match_complete_probability = 200;
-    static_assert(dev_prerender_enabled_probability +
-                  dev_control_probability +
-                  dev_experiment_multi_prerender_probability +
-                  dev_experiment_15min_ttl_probability +
-                  dev_experiment_no_use_probability +
-                  dev_experiment_match_complete_probability == divisor,
-                  "dev experiment probabilities must equal divisor");
-
-    control_probability = dev_control_probability;
-    experiment_multi_prerender_probability =
-        dev_experiment_multi_prerender_probability;
-    experiment_15min_ttl_probability = dev_experiment_15min_ttl_probability;
-    experiment_no_use_probability = dev_experiment_no_use_probability;
-    experiment_match_complete_probability =
-        dev_experiment_match_complete_probability;
-  }
-
-  int prerender_enabled_group = -1;
-  scoped_refptr<FieldTrial> trial(
-      FieldTrialList::FactoryGetFieldTrial(
-          "Prerender", divisor, "PrerenderEnabled",
-          2014, 12, 31, FieldTrial::SESSION_RANDOMIZED,
-          &prerender_enabled_group));
-  const int control_group =
-      trial->AppendGroup("PrerenderControl",
-                         control_probability);
-  const int experiment_multi_prerender_group =
-      trial->AppendGroup("PrerenderMulti",
-                         experiment_multi_prerender_probability);
-  const int experiment_15_min_TTL_group =
-      trial->AppendGroup("Prerender15minTTL",
-                         experiment_15min_ttl_probability);
-  const int experiment_no_use_group =
-      trial->AppendGroup("PrerenderNoUse",
-                         experiment_no_use_probability);
-  const int experiment_match_complete_group =
-      trial->AppendGroup("MatchComplete",
-                         experiment_match_complete_probability);
-
-  const int trial_group = trial->group();
-  if (trial_group == prerender_enabled_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP);
-  } else if (trial_group == control_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP);
-  } else if (trial_group == experiment_multi_prerender_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP);
-  } else if (trial_group == experiment_15_min_TTL_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP);
-  } else if (trial_group == experiment_no_use_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP);
-  } else if (trial_group == experiment_match_complete_group) {
-    PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_MATCH_COMPLETE_GROUP);
-  } else {
-    NOTREACHED();
-  }
-}
 
 }  // end namespace
 
 void ConfigurePrerender(const base::CommandLine& command_line) {
-  enum PrerenderOption {
-    PRERENDER_OPTION_AUTO,
-    PRERENDER_OPTION_DISABLED,
-    PRERENDER_OPTION_ENABLED,
-  };
-
-  PrerenderOption prerender_option = PRERENDER_OPTION_AUTO;
+  PrerenderManager::PrerenderManagerMode mode =
+      PrerenderManager::PRERENDER_MODE_ENABLED;
   if (command_line.HasSwitch(switches::kPrerenderMode)) {
     const string switch_value =
         command_line.GetSwitchValueASCII(switches::kPrerenderMode);
 
-    if (switch_value == switches::kPrerenderModeSwitchValueAuto) {
-      prerender_option = PRERENDER_OPTION_AUTO;
-    } else if (switch_value == switches::kPrerenderModeSwitchValueDisabled) {
-      prerender_option = PRERENDER_OPTION_DISABLED;
+    if (switch_value == switches::kPrerenderModeSwitchValueDisabled) {
+      mode = PrerenderManager::PRERENDER_MODE_DISABLED;
     } else if (switch_value.empty() ||
                switch_value == switches::kPrerenderModeSwitchValueEnabled) {
       // The empty string means the option was provided with no value, and that
       // means enable.
-      prerender_option = PRERENDER_OPTION_ENABLED;
+      mode = PrerenderManager::PRERENDER_MODE_ENABLED;
     } else {
-      prerender_option = PRERENDER_OPTION_DISABLED;
+      mode = PrerenderManager::PRERENDER_MODE_DISABLED;
       LOG(ERROR) << "Invalid --prerender option received on command line: "
                  << switch_value;
       LOG(ERROR) << "Disabling prerendering!";
     }
   }
 
-  switch (prerender_option) {
-    case PRERENDER_OPTION_AUTO:
-      SetupPrerenderFieldTrial();
-      break;
-    case PRERENDER_OPTION_DISABLED:
-      PrerenderManager::SetMode(PrerenderManager::PRERENDER_MODE_DISABLED);
-      break;
-    case PRERENDER_OPTION_ENABLED:
-      PrerenderManager::SetMode(PrerenderManager::PRERENDER_MODE_ENABLED);
-      break;
-    default:
-      NOTREACHED();
-  }
+  PrerenderManager::SetMode(mode);
 }
 
 bool IsOmniboxEnabled(Profile* profile) {
@@ -261,31 +75,10 @@ bool IsOmniboxEnabled(Profile* profile) {
     DCHECK_EQ(switches::kPrerenderFromOmniboxSwitchValueAuto, switch_value);
   }
 
-  return (FieldTrialList::FindFullName("PrerenderFromOmnibox") !=
+  return (base::FieldTrialList::FindFullName("PrerenderFromOmnibox") !=
           "OmniboxPrerenderDisabled");
 }
 
-/*
-PrerenderLocalPredictorSpec is a field trial, and its value must have the
-following format:
-key1=value1:key2=value2:key3=value3
-eg "LocalPredictor=Enabled:SideEffectFreeWhitelist=Enabled"
-The function below extracts the value corresponding to a key provided from the
-LocalPredictorSpec.
-*/
-string GetLocalPredictorSpecValue(string spec_key) {
-  vector<string> elements;
-  base::SplitString(FieldTrialList::FindFullName(kLocalPredictorSpecTrialName),
-                    ':', &elements);
-  for (int i = 0; i < static_cast<int>(elements.size()); i++) {
-    vector<string> key_value;
-    base::SplitString(elements[i], '=', &key_value);
-    if (key_value.size() == 2 && key_value[0] == spec_key)
-      return key_value[1];
-  }
-  return string();
-}
-
 bool IsUnencryptedSyncEnabled(Profile* profile) {
   ProfileSyncService* service = ProfileSyncServiceFactory::GetInstance()->
       GetForProfile(profile);
@@ -296,44 +89,15 @@ bool IsUnencryptedSyncEnabled(Profile* profile) {
 // Indicates whether the Local Predictor is enabled based on field trial
 // selection.
 bool IsLocalPredictorEnabled() {
-#if defined(OS_ANDROID) || defined(OS_IOS)
   return false;
-#endif
-  return !base::CommandLine::ForCurrentProcess()->HasSwitch(
-             switches::kDisablePrerenderLocalPredictor) &&
-         GetLocalPredictorSpecValue(kLocalPredictorKeyName) == kEnabledGroup;
 }
 
 bool ShouldDisableLocalPredictorBasedOnSyncAndConfiguration(Profile* profile) {
-  return
-      GetLocalPredictorSpecValue(kLocalPredictorUnencryptedSyncOnlyKeyName) ==
-          kEnabledGroup &&
-      !IsUnencryptedSyncEnabled(profile);
+  return false;
 }
 
 bool ShouldDisableLocalPredictorDueToPreferencesAndNetwork(Profile* profile) {
-  bool on_cellular =
-      net::NetworkChangeNotifier::IsConnectionCellular(
-          net::NetworkChangeNotifier::GetConnectionType());
-  // If the user is not on a cellular connection, but we require a cellular
-  // connection, we must temporarily disable our local predictions.
-  if (!on_cellular &&
-      GetLocalPredictorSpecValue(kLocalPredictorOnCellularOnly) ==
-      kEnabledGroup) {
-    return true;
-  }
-
-  // If we don't care whether or not network prediction will actually be
-  // exercised, we do not need to temporarily disable our predictions.
-  if (GetLocalPredictorSpecValue(kLocalPredictorNetworkPredictionEnabledOnly) !=
-      kEnabledGroup) {
-    return false;
-  }
-
-  // We should temporarily disable iff the predictive network action would
-  // not be exercised.
-
-  return !chrome_browser_net::CanPrefetchAndPrerenderUI(profile->GetPrefs());
+  return false;
 }
 
 bool IsLoggedInPredictorEnabled() {
@@ -341,140 +105,98 @@ bool IsLoggedInPredictorEnabled() {
 }
 
 bool IsSideEffectFreeWhitelistEnabled() {
-  return IsLocalPredictorEnabled() &&
-      GetLocalPredictorSpecValue(kSideEffectFreeWhitelistKeyName) !=
-      kDisabledGroup;
+  return IsLocalPredictorEnabled();
 }
 
 bool IsLocalPredictorPrerenderLaunchEnabled() {
-  return GetLocalPredictorSpecValue(kPrerenderLaunchKeyName) != kDisabledGroup;
+  return true;
 }
 
 bool IsLocalPredictorPrerenderAlwaysControlEnabled() {
   // If we prefetch rather than prerender, we automatically also prerender
   // as a control group only.
-  return (GetLocalPredictorSpecValue(kPrerenderAlwaysControlKeyName) ==
-          kEnabledGroup) || IsLocalPredictorPrerenderPrefetchEnabled();
+  return IsLocalPredictorPrerenderPrefetchEnabled();
 }
 
 bool IsLocalPredictorPrerenderPrefetchEnabled() {
-  return GetLocalPredictorSpecValue(kPrerenderPrefetchKeyName) ==
-      kEnabledGroup;
+  return false;
 }
 
 bool ShouldQueryPrerenderService(Profile* profile) {
-  return IsUnencryptedSyncEnabled(profile) &&
-      GetLocalPredictorSpecValue(kPrerenderQueryPrerenderServiceKeyName) ==
-      kEnabledGroup;
+  return false;
 }
 
 bool ShouldQueryPrerenderServiceForCurrentURL() {
-  return GetLocalPredictorSpecValue(
-      kPrerenderQueryPrerenderServiceCurrentURLKeyName) != kDisabledGroup;
+  return true;
 }
 
 bool ShouldQueryPrerenderServiceForCandidateURLs() {
-  return GetLocalPredictorSpecValue(
-      kPrerenderQueryPrerenderServiceCandidateURLsKeyName) != kDisabledGroup;
+  return true;
 }
 
 string GetPrerenderServiceURLPrefix() {
-  string prefix = variations::GetVariationParamValue(
-      kLocalPredictorSpecTrialName,
-      kPrerenderServiceURLPrefixParameterName);
-  return prefix.empty() ? kDefaultPrerenderServiceURLPrefix : prefix;
+  return kDefaultPrerenderServiceURLPrefix;
 }
 
 int GetPrerenderServiceBehaviorID() {
-  int id;
-  StringToInt(GetLocalPredictorSpecValue(kPrerenderServiceBehaviorIDKeyName),
-              &id);
-  // The behavior ID must be non-negative.
-  return std::max(id, 0);
+  return 0;
 }
 
 int GetPrerenderServiceFetchTimeoutMs() {
-  int result;
-  StringToInt(GetLocalPredictorSpecValue(kPrerenderServiceFetchTimeoutKeyName),
-              &result);
-  // If the value is outside the valid range, use the default value.
-  return (result < kMinPrerenderServiceTimeoutMs ||
-          result > kMaxPrerenderServiceTimeoutMs) ?
-      kDefaultPrerenderServiceTimeoutMs : result;
+  return kDefaultPrerenderServiceTimeoutMs;
 }
 
 int GetPrerenderPrefetchListTimeoutSeconds() {
-  int result;
-  StringToInt(GetLocalPredictorSpecValue(kPrefetchListTimeoutKeyName), &result);
-  // If the value is outside the valid range, use the default value.
-  return (result < kMinPrefetchListTimeoutSeconds ||
-          result > kMaxPrefetchListTimeoutSeconds) ?
-      kDefaultPrefetchListTimeoutSeconds : result;
+  return kDefaultPrefetchListTimeoutSeconds;
 }
 
 int GetLocalPredictorTTLSeconds() {
-  int ttl;
-  StringToInt(GetLocalPredictorSpecValue(kPrerenderTTLKeyName), &ttl);
-  // If the value is outside of 10s or 600s, use a default value of 180s.
-  return (ttl < 10 || ttl > 600) ? 180 : ttl;
+  // Use a default value of 180s.
+  return 180;
 }
 
 int GetLocalPredictorPrerenderPriorityHalfLifeTimeSeconds() {
-  int half_life_time;
-  StringToInt(GetLocalPredictorSpecValue(kPrerenderPriorityHalfLifeTimeKeyName),
-              &half_life_time);
-  // Sanity check: Ensure the half life time is non-negative.
-  return std::max(half_life_time, 0);
+  return 0;
 }
 
 int GetLocalPredictorMaxConcurrentPrerenders() {
-  int num_prerenders;
-  StringToInt(GetLocalPredictorSpecValue(kMaxConcurrentPrerenderKeyName),
-              &num_prerenders);
-  // Sanity check: Ensure the number of prerenders is between 1 and 10.
-  return std::min(std::max(num_prerenders, 1), 10);
+  return 1;
 }
 
 int GetLocalPredictorMaxLaunchPrerenders() {
-  int num_prerenders;
-  StringToInt(GetLocalPredictorSpecValue(kMaxLaunchPrerenderKeyName),
-              &num_prerenders);
-  // Sanity check: Ensure the number of prerenders is between 1 and 10.
-  return std::min(std::max(num_prerenders, 1), 10);
+  return 1;
 }
 
 bool SkipLocalPredictorFragment() {
-  return GetLocalPredictorSpecValue(kSkipFragment) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorHTTPS() {
-  return GetLocalPredictorSpecValue(kSkipHTTPS) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorWhitelist() {
-  return GetLocalPredictorSpecValue(kSkipWhitelist) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorServiceWhitelist() {
-  return GetLocalPredictorSpecValue(kSkipServiceWhitelist) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorLoggedIn() {
-  return GetLocalPredictorSpecValue(kSkipLoggedIn) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorDefaultNoPrerender() {
-  return GetLocalPredictorSpecValue(kSkipDefaultNoPrerender) == kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorLocalCandidates() {
-  return GetLocalPredictorSpecValue(kSkipPrerenderLocalCanadidates) ==
-      kEnabledGroup;
+  return false;
 }
 
 bool SkipLocalPredictorServiceCandidates() {
-  return GetLocalPredictorSpecValue(kSkipPrerenderServiceCanadidates) ==
-      kEnabledGroup;
+  return false;
 }
 
 }  // namespace prerender