Make field trial randomization type a constructor param.

Changes the Field Trial API to require users to pass ONE_TIME_RANDOMIZED
or SESSION_RANDOMIZED at the time the field trial is created.

This removes a source of human errors, where developers would sometimes
previously forget to call UseOneTimeRandomization() in their CLs.

It's a small startup performance win, since one time randomized trials will
no longer call RandDouble() that will be then replaced by a value from the
entropy provider. (This was showing up in profiles when I was measuring
metrics startup perf on mobile.)

BUG=262971
TEST=Existing unit tests.
TBR=isherman@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/20777005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214352 0039d316-1c4b-4281-b951-d872f2087c98

17 files changed, 135 insertions, 143 deletions

diff --git a/chrome/browser/chrome_browser_field_trials_desktop.cc b/chrome/browser/chrome_browser_field_trials_desktop.cc
index 339ee6b..92b6645 100644
--- a/chrome/browser/chrome_browser_field_trials_desktop.cc
+++ b/chrome/browser/chrome_browser_field_trials_desktop.cc
@@ -62,9 +62,9 @@ void SetupInfiniteCacheFieldTrial() {
   base::FieldTrial::Probability infinite_cache_probability = 0;
 
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial("InfiniteCache", kDivisor,
-                                                 "No", 2013, 12, 31, NULL));
-  trial->UseOneTimeRandomization();
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "InfiniteCache", kDivisor, "No", 2013, 12, 31,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
   trial->AppendGroup("Yes", infinite_cache_probability);
   trial->AppendGroup("Control", infinite_cache_probability);
 }
@@ -106,9 +106,9 @@ void SetupCacheSensitivityAnalysisFieldTrial() {
 #endif
 
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial("CacheSensitivityAnalysis",
-                                                 kDivisor, "No",
-                                                 2013, 06, 15, NULL));
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "CacheSensitivityAnalysis", kDivisor, "No", 2013, 06, 15,
+          base::FieldTrial::SESSION_RANDOMIZED, NULL));
   trial->AppendGroup("ControlA", sensitivity_analysis_probability);
   trial->AppendGroup("ControlB", sensitivity_analysis_probability);
   trial->AppendGroup("100A", sensitivity_analysis_probability);
@@ -130,8 +130,9 @@ void WindowsOverlappedTCPReadsFieldTrial(
     const base::FieldTrial::Probability kDivisor = 2;  // 1 in 2 chance
     const base::FieldTrial::Probability kOverlappedReadProbability = 1;
     scoped_refptr<base::FieldTrial> overlapped_reads_trial(
-        base::FieldTrialList::FactoryGetFieldTrial("OverlappedReadImpact",
-            kDivisor, "OverlappedReadEnabled", 2013, 6, 1, NULL));
+        base::FieldTrialList::FactoryGetFieldTrial(
+            "OverlappedReadImpact", kDivisor, "OverlappedReadEnabled",
+            2013, 6, 1, base::FieldTrial::SESSION_RANDOMIZED, NULL));
     int overlapped_reads_disabled_group =
         overlapped_reads_trial->AppendGroup("OverlappedReadDisabled",
                                             kOverlappedReadProbability);
@@ -145,8 +146,8 @@ void WindowsOverlappedTCPReadsFieldTrial(
 void SetupLowLatencyFlashAudioFieldTrial() {
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
-          content::kLowLatencyFlashAudioFieldTrialName,
-          100, "Standard", 2013, 9, 1, NULL));
+          content::kLowLatencyFlashAudioFieldTrialName, 100, "Standard",
+          2013, 9, 1, base::FieldTrial::SESSION_RANDOMIZED, NULL));
 
   // Trial is enabled for dev / beta / canary users only.
   if (chrome::VersionInfo::GetChannel() != chrome::VersionInfo::CHANNEL_STABLE)
diff --git a/chrome/browser/chrome_browser_field_trials_mobile.cc b/chrome/browser/chrome_browser_field_trials_mobile.cc
index 5e17ca7..8d9140c 100644
--- a/chrome/browser/chrome_browser_field_trials_mobile.cc
+++ b/chrome/browser/chrome_browser_field_trials_mobile.cc
@@ -37,10 +37,8 @@ void DataCompressionProxyFieldTrial() {
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
           kDataCompressionProxyFieldTrialName, kDataCompressionProxyDivisor,
-          kDisabled, 2015, 1, 1, NULL));
+          kDisabled, 2015, 1, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
 
-  // We want our trial results to be persistent.
-  trial->UseOneTimeRandomization();
   // Non-stable channels will run with probability 1.
   const int kEnabledGroup = trial->AppendGroup(
       kEnabled,
@@ -77,10 +75,8 @@ void NewTabButtonInToolbarFieldTrial(const CommandLine& parsed_command_line) {
       base::FieldTrialList::FactoryGetFieldTrial(
           kPhoneNewTabToolbarButtonFieldTrialName,
           kPhoneNewTabToolbarButtonDivisor,
-          kDisabled, 2015, 1, 1, NULL));
+          kDisabled, 2015, 1, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
 
-  // We want our trial results to be persistent.
-  trial->UseOneTimeRandomization();
   const int kEnabledGroup = trial->AppendGroup(
       kEnabled,
       kIsStableChannel ?
diff --git a/chrome/browser/chromeos/external_metrics.cc b/chrome/browser/chromeos/external_metrics.cc
index cabac24..5c6b329 100644
--- a/chrome/browser/chromeos/external_metrics.cc
+++ b/chrome/browser/chromeos/external_metrics.cc
@@ -63,10 +63,10 @@ void SetupProgressiveScanFieldTrial() {
   const char path_to_group_file[] = "/home/chronos/.progressive_scan_variation";
   const base::FieldTrial::Probability kDivisor = 1000;
   scoped_refptr<base::FieldTrial> trial =
-      base::FieldTrialList::FactoryGetFieldTrial(name_of_experiment,
-                                                 kDivisor,
-                                                 "Default",
-                                                 2013, 12, 31, NULL);
+      base::FieldTrialList::FactoryGetFieldTrial(
+          name_of_experiment, kDivisor, "Default", 2013, 12, 31,
+          base::FieldTrial::SESSION_RANDOMIZED, NULL);
+
   // Announce the groups with 0 percentage; the actual percentages come from
   // the server configuration.
   std::map<int, std::string> group_to_char;
@@ -113,10 +113,10 @@ void SetupSwapJankFieldTrial() {
   // All groups are either on or off.
   const base::FieldTrial::Probability kTotalProbability = 1;
   scoped_refptr<base::FieldTrial> trial =
-      base::FieldTrialList::FactoryGetFieldTrial(name_of_experiment,
-                                                 kTotalProbability,
-                                                 "default",
-                                                 2013, 12, 31, NULL);
+      base::FieldTrialList::FactoryGetFieldTrial(
+          name_of_experiment, kTotalProbability, "default", 2013, 12, 31,
+          base::FieldTrial::SESSION_RANDOMIZED, NULL);
+
   // Assign probability of 1 to this Chrome's group.  Assign 0 to all other
   // choices.
   trial->AppendGroup("kernel_64_chrome_64",
diff --git a/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc b/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
index c75234a..f6de0e0 100644
--- a/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
+++ b/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
@@ -134,8 +134,8 @@ void SetupTrial() {
   const base::FieldTrial::Probability kDivisor = 100;
   scoped_refptr<base::FieldTrial> trial =
       base::FieldTrialList::FactoryGetFieldTrial(
-          kExperimentName, kDivisor, "Existing", 2013, 12, 31, NULL);
-  trial->UseOneTimeRandomization();
+          kExperimentName, kDivisor, "Existing", 2013, 12, 31,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL);
 
   // Split 50/50 between "Control" and "Alternamte" group for new user.
   // Existing users already have their default pinned apps and have the trial
diff --git a/chrome/browser/gpu/chrome_gpu_util.cc b/chrome/browser/gpu/chrome_gpu_util.cc
index 441cebc..61da773 100644
--- a/chrome/browser/gpu/chrome_gpu_util.cc
+++ b/chrome/browser/gpu/chrome_gpu_util.cc
@@ -99,11 +99,8 @@ void InitializeCompositingFieldTrial() {
   const base::FieldTrial::Probability kDivisor = 3;
   scoped_refptr<base::FieldTrial> trial(
     base::FieldTrialList::FactoryGetFieldTrial(
-        content::kGpuCompositingFieldTrialName, kDivisor,
-        "disable", 2013, 12, 31, NULL));
-
-  // Produce the same result on every run of this client.
-  trial->UseOneTimeRandomization();
+        content::kGpuCompositingFieldTrialName, kDivisor,  "disable",
+        2013, 12, 31, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
 
   base::FieldTrial::Probability force_compositing_mode_probability = 0;
   base::FieldTrial::Probability threaded_compositing_probability = 0;
@@ -131,5 +128,5 @@ void InitializeCompositingFieldTrial() {
   UMA_HISTOGRAM_BOOLEAN("GPU.InCompositorThreadFieldTrial", thread);
 }
 
-}  // namespace gpu_util;
+}  // namespace gpu_util
 
diff --git a/chrome/browser/metrics/gzipped_protobufs_field_trial.cc b/chrome/browser/metrics/gzipped_protobufs_field_trial.cc
index cd105be..81c34f7 100644
--- a/chrome/browser/metrics/gzipped_protobufs_field_trial.cc
+++ b/chrome/browser/metrics/gzipped_protobufs_field_trial.cc
@@ -39,8 +39,8 @@ void CreateGzippedProtobufsFieldTrial() {
           2013,
           10,
           1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED,
           NULL);
-  gzipped_protobufs_trial->UseOneTimeRandomization();
   int gzipped_protobufs_group = gzipped_protobufs_trial->AppendGroup(
       kGroupName,
       kTrialQuotient);
diff --git a/chrome/browser/metrics/thread_watcher.cc b/chrome/browser/metrics/thread_watcher.cc
index c8ee4cf..4a14015 100644
--- a/chrome/browser/metrics/thread_watcher.cc
+++ b/chrome/browser/metrics/thread_watcher.cc
@@ -569,7 +569,7 @@ void ThreadWatcherList::ParseCommandLine(
   scoped_refptr<base::FieldTrial> field_trial(
       base::FieldTrialList::FactoryGetFieldTrial(
           "ThreadWatcher", 100, "default_hung_threads",
-          2013, 10, 30, NULL));
+          2013, 10, 30, base::FieldTrial::SESSION_RANDOMIZED, NULL));
   int hung_thread_group = field_trial->AppendGroup("hung_thread", 100);
   if (field_trial->group() == hung_thread_group) {
     for (CrashOnHangThreadMap::iterator it = crash_on_hang_threads->begin();
diff --git a/chrome/browser/metrics/variations/variations_seed_processor.cc b/chrome/browser/metrics/variations/variations_seed_processor.cc
index 58161f2..ef98d85 100644
--- a/chrome/browser/metrics/variations/variations_seed_processor.cc
+++ b/chrome/browser/metrics/variations/variations_seed_processor.cc
@@ -181,21 +181,24 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
     }
   }
 
+  uint32 randomization_seed = 0;
+  base::FieldTrial::RandomizationType randomization_type =
+      base::FieldTrial::SESSION_RANDOMIZED;
+  if (study.has_consistency() &&
+      study.consistency() == Study_Consistency_PERMANENT) {
+    randomization_type = base::FieldTrial::ONE_TIME_RANDOMIZED;
+    if (study.has_randomization_seed())
+      randomization_seed = study.randomization_seed();
+  }
+
   // The trial is created without specifying an expiration date because the
   // expiration check in field_trial.cc is based on the build date. Instead,
   // the expiration check using |reference_date| is done explicitly below.
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial(
+      base::FieldTrialList::FactoryGetFieldTrialWithRandomizationSeed(
           study.name(), total_probability, study.default_experiment_name(),
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL));
-
-  if (study.has_consistency() &&
-      study.consistency() == Study_Consistency_PERMANENT) {
-    if (study.has_randomization_seed())
-      trial->UseOneTimeRandomizationWithCustomSeed(study.randomization_seed());
-    else
-      trial->UseOneTimeRandomization();
-  }
+          base::FieldTrialList::kNoExpirationYear, 1, 1, randomization_type,
+          randomization_seed, NULL));
 
   for (int i = 0; i < study.experiment_size(); ++i) {
     const Study_Experiment& experiment = study.experiment(i);
diff --git a/chrome/browser/net/http_pipelining_compatibility_client.cc b/chrome/browser/net/http_pipelining_compatibility_client.cc
index 042a5a2..e90fb03 100644
--- a/chrome/browser/net/http_pipelining_compatibility_client.cc
+++ b/chrome/browser/net/http_pipelining_compatibility_client.cc
@@ -465,7 +465,8 @@ void CollectPipeliningCapabilityStatsOnIOThread(
   }
   // After May 4, 2012, the trial will disable itself.
   trial = base::FieldTrialList::FactoryGetFieldTrial(
-      kTrialName, kDivisor, "disable_test", 2012, 5, 4, NULL);
+      kTrialName, kDivisor, "disable_test", 2012, 5, 4,
+      base::FieldTrial::SESSION_RANDOMIZED, NULL);
 
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_CANARY) {
diff --git a/chrome/browser/net/network_stats.cc b/chrome/browser/net/network_stats.cc
index f9a4f2e..8a9fe1f 100644
--- a/chrome/browser/net/network_stats.cc
+++ b/chrome/browser/net/network_stats.cc
@@ -806,13 +806,9 @@ void CollectNetworkStats(const std::string& network_stats_server,
 
     // After July 31, 2014 builds, it will always be in default group
     // (disable_network_stats).
-    trial = base::FieldTrialList::FactoryGetFieldTrial("NetworkConnectivity",
-                                                       kDivisor,
-                                                       "disable_network_stats",
-                                                       2014,
-                                                       7,
-                                                       31,
-                                                       NULL);
+    trial = base::FieldTrialList::FactoryGetFieldTrial(
+        "NetworkConnectivity", kDivisor, "disable_network_stats",
+        2014, 7, 31, base::FieldTrial::SESSION_RANDOMIZED, NULL);
 
     // Add option to collect_stats for NetworkConnectivity.
     int collect_stats_group =
diff --git a/chrome/browser/omnibox/omnibox_field_trial.cc b/chrome/browser/omnibox/omnibox_field_trial.cc
index 0fbf10d..09c2d1a 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.cc
+++ b/chrome/browser/omnibox/omnibox_field_trial.cc
@@ -87,9 +87,8 @@ void OmniboxFieldTrial::ActivateStaticTrials() {
   // Make it expire on March 1, 2013.
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
-      kHUPCullRedirectsFieldTrialName, kHUPCullRedirectsFieldTrialDivisor,
-      "Standard", 2013, 3, 1, NULL));
-  trial->UseOneTimeRandomization();
+          kHUPCullRedirectsFieldTrialName, kHUPCullRedirectsFieldTrialDivisor,
+          "Standard", 2013, 3, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
   hup_dont_cull_redirects_experiment_group =
       trial->AppendGroup("DontCullRedirects",
                          kHUPCullRedirectsFieldTrialExperimentFraction);
@@ -98,8 +97,8 @@ void OmniboxFieldTrial::ActivateStaticTrials() {
   // Make it expire on March 1, 2013.
   trial = base::FieldTrialList::FactoryGetFieldTrial(
       kHUPCreateShorterMatchFieldTrialName,
-      kHUPCreateShorterMatchFieldTrialDivisor, "Standard", 2013, 3, 1, NULL);
-  trial->UseOneTimeRandomization();
+      kHUPCreateShorterMatchFieldTrialDivisor, "Standard", 2013, 3, 1,
+      base::FieldTrial::ONE_TIME_RANDOMIZED, NULL);
   hup_dont_create_shorter_match_experiment_group =
       trial->AppendGroup("DontCreateShorterMatch",
                          kHUPCreateShorterMatchFieldTrialExperimentFraction);
diff --git a/chrome/browser/password_manager/password_manager.cc b/chrome/browser/password_manager/password_manager.cc
index e1390aa..dbeec6b 100644
--- a/chrome/browser/password_manager/password_manager.cc
+++ b/chrome/browser/password_manager/password_manager.cc
@@ -311,8 +311,8 @@ void PasswordManager::OnPasswordFormsRendered(
   if (provisional_save_manager_->HasGeneratedPassword())
     UMA_HISTOGRAM_COUNTS("PasswordGeneration.Submitted", 1);
 
-  if(!CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kEnableSavePasswordBubble)){
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableSavePasswordBubble)) {
     if (ShouldShowSavePasswordInfoBar()) {
       delegate_->AddSavePasswordInfoBarIfPermitted(
           provisional_save_manager_.release());
@@ -344,8 +344,8 @@ void PasswordManager::PossiblyInitializeUsernamesExperiment(
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
           kOtherPossibleUsernamesExperiment,
-          kDivisor, "Disabled", 2013, 12, 31, NULL));
-  trial->UseOneTimeRandomization();
+          kDivisor, "Disabled", 2013, 12, 31,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
   base::FieldTrial::Probability enabled_probability = 0;
 
   switch (chrome::VersionInfo::GetChannel()) {
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index ca12522..4d04ff6 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -56,7 +56,7 @@ void SetupPrefetchFieldTrial() {
   scoped_refptr<FieldTrial> trial(
       FieldTrialList::FactoryGetFieldTrial(
           "Prefetch", divisor, "ContentPrefetchPrefetchOff",
-          2013, 12, 31, NULL));
+          2013, 12, 31, FieldTrial::SESSION_RANDOMIZED, NULL));
   const int kPrefetchOnGroup = trial->AppendGroup("ContentPrefetchPrefetchOn",
                                                   prefetch_probability);
   PrerenderManager::SetIsPrefetchEnabled(trial->group() == kPrefetchOnGroup);
@@ -118,7 +118,8 @@ void SetupPrerenderFieldTrial() {
   scoped_refptr<FieldTrial> trial(
       FieldTrialList::FactoryGetFieldTrial(
           "Prerender", divisor, "PrerenderEnabled",
-          2013, 12, 31, &prerender_enabled_group));
+          2013, 12, 31, FieldTrial::SESSION_RANDOMIZED,
+          &prerender_enabled_group));
   const int control_group =
       trial->AppendGroup("PrerenderControl",
                          control_probability);
@@ -229,7 +230,8 @@ void ConfigureOmniboxPrerender() {
   scoped_refptr<FieldTrial> omnibox_prerender_trial(
       FieldTrialList::FactoryGetFieldTrial(
           kOmniboxTrialName, kDivisor, "OmniboxPrerenderEnabled",
-          2013, 12, 31, &g_omnibox_trial_default_group_number));
+          2013, 12, 31, FieldTrial::SESSION_RANDOMIZED,
+          &g_omnibox_trial_default_group_number));
   omnibox_prerender_trial->AppendGroup("OmniboxPrerenderDisabled",
                                        kDisabledProbability);
 }
@@ -242,7 +244,8 @@ void ConfigureLocalPredictor() {
   }
   scoped_refptr<FieldTrial> local_predictor_trial(
       FieldTrialList::FactoryGetFieldTrial(
-          kLocalPredictorTrialName, 100, kDisabledGroup, 2013, 12, 31, NULL));
+          kLocalPredictorTrialName, 100, kDisabledGroup, 2013, 12, 31,
+          FieldTrial::SESSION_RANDOMIZED, NULL));
   local_predictor_trial->AppendGroup(kEnabledGroup, 100);
 }
 
diff --git a/chrome/browser/ui/bookmarks/bookmark_prompt_controller.cc b/chrome/browser/ui/bookmarks/bookmark_prompt_controller.cc
index 9986383..6013a1b 100644
--- a/chrome/browser/ui/bookmarks/bookmark_prompt_controller.cc
+++ b/chrome/browser/ui/bookmarks/bookmark_prompt_controller.cc
@@ -229,8 +229,9 @@ bool BookmarkPromptController::IsEnabled() {
           kBookmarkPromptTrialName, 100, kBookmarkPromptDefaultGroup,
           date_range->expiration_date.year,
           date_range->expiration_date.month,
-          date_range->expiration_date.day_of_month, NULL));
-  trial->UseOneTimeRandomization();
+          date_range->expiration_date.day_of_month,
+          base::FieldTrial::ONE_TIME_RANDOMIZED,
+          NULL));
   trial->AppendGroup(kBookmarkPromptControlGroup, 10);
   trial->AppendGroup(kBookmarkPromptExperimentGroup, 10);
 
diff --git a/chrome/common/metrics/entropy_provider_unittest.cc b/chrome/common/metrics/entropy_provider_unittest.cc
index e64a8eb..5c54128 100644
--- a/chrome/common/metrics/entropy_provider_unittest.cc
+++ b/chrome/common/metrics/entropy_provider_unittest.cc
@@ -193,15 +193,17 @@ TEST_F(EntropyProviderTest, UseOneTimeRandomizationSHA1) {
   // _might_ actually give the same result, but we know that given
   // the particular client_id we use for unit tests they won't.
   base::FieldTrialList field_trial_list(new SHA1EntropyProvider("client_id"));
+  const int kNoExpirationYear = base::FieldTrialList::kNoExpirationYear;
   scoped_refptr<base::FieldTrial> trials[] = {
-      base::FieldTrialList::FactoryGetFieldTrial("one", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL),
-      base::FieldTrialList::FactoryGetFieldTrial("two", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL) };
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "one", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL),
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "two", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL),
+  };
 
   for (size_t i = 0; i < arraysize(trials); ++i) {
-    trials[i]->UseOneTimeRandomization();
-
     for (int j = 0; j < 100; ++j)
       trials[i]->AppendGroup(std::string(), 1);
   }
@@ -221,15 +223,17 @@ TEST_F(EntropyProviderTest, UseOneTimeRandomizationPermuted) {
   // the particular client_id we use for unit tests they won't.
   base::FieldTrialList field_trial_list(
       new PermutedEntropyProvider(1234, kMaxLowEntropySize));
+  const int kNoExpirationYear = base::FieldTrialList::kNoExpirationYear;
   scoped_refptr<base::FieldTrial> trials[] = {
-      base::FieldTrialList::FactoryGetFieldTrial("one", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL),
-      base::FieldTrialList::FactoryGetFieldTrial("two", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL) };
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "one", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL),
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "two", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL),
+  };
 
   for (size_t i = 0; i < arraysize(trials); ++i) {
-    trials[i]->UseOneTimeRandomization();
-
     for (int j = 0; j < 100; ++j)
       trials[i]->AppendGroup(std::string(), 1);
   }
@@ -245,16 +249,18 @@ TEST_F(EntropyProviderTest, UseOneTimeRandomizationWithCustomSeedPermuted) {
   // for one time randomization produce the same group assignments.
   base::FieldTrialList field_trial_list(
       new PermutedEntropyProvider(1234, kMaxLowEntropySize));
-  scoped_refptr<base::FieldTrial> trials[] = {
-      base::FieldTrialList::FactoryGetFieldTrial("one", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL),
-      base::FieldTrialList::FactoryGetFieldTrial("two", 100, "default",
-          base::FieldTrialList::kNoExpirationYear, 1, 1, NULL) };
+  const int kNoExpirationYear = base::FieldTrialList::kNoExpirationYear;
   const uint32 kCustomSeed = 9001;
+  scoped_refptr<base::FieldTrial> trials[] = {
+      base::FieldTrialList::FactoryGetFieldTrialWithRandomizationSeed(
+          "one", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, kCustomSeed, NULL),
+      base::FieldTrialList::FactoryGetFieldTrialWithRandomizationSeed(
+          "two", 100, "default", kNoExpirationYear, 1, 1,
+          base::FieldTrial::ONE_TIME_RANDOMIZED, kCustomSeed, NULL),
+  };
 
   for (size_t i = 0; i < arraysize(trials); ++i) {
-    trials[i]->UseOneTimeRandomizationWithCustomSeed(kCustomSeed);
-
     for (int j = 0; j < 100; ++j)
       trials[i]->AppendGroup(std::string(), 1);
   }
diff --git a/chrome/common/metrics/variations/uniformity_field_trials.cc b/chrome/common/metrics/variations/uniformity_field_trials.cc
index 0ae53a5..a51da1e 100644
--- a/chrome/common/metrics/variations/uniformity_field_trials.cc
+++ b/chrome/common/metrics/variations/uniformity_field_trials.cc
@@ -9,6 +9,8 @@
 #include "base/time/time.h"
 #include "chrome/common/metrics/variations/variations_util.h"
 
+namespace chrome_variations {
+
 namespace {
 
 // Set up a uniformity field trial. |one_time_randomized| indicates if the
@@ -16,9 +18,9 @@ namespace {
 // must contain a "%d" since the percentage of the group will be inserted in
 // the trial name. |num_trial_groups| must be a divisor of 100 (e.g. 5, 20)
 void SetupSingleUniformityFieldTrial(
-    bool one_time_randomized,
+    base::FieldTrial::RandomizationType randomization_type,
     const std::string& trial_name_string,
-    const chrome_variations::VariationID trial_base_id,
+    const VariationID trial_base_id,
     int num_trial_groups) {
   // Probability per group remains constant for all uniformity trials, what
   // changes is the probability divisor.
@@ -35,12 +37,10 @@ void SetupSingleUniformityFieldTrial(
 
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
-          trial_name, divisor, kDefaultGroupName, 2015, 1, 1, NULL));
-  if (one_time_randomized)
-    trial->UseOneTimeRandomization();
-  chrome_variations::AssociateGoogleVariationID(
-      chrome_variations::GOOGLE_UPDATE_SERVICE, trial_name, kDefaultGroupName,
-      trial_base_id);
+          trial_name, divisor, kDefaultGroupName, 2015, 1, 1,
+          randomization_type, NULL));
+  AssociateGoogleVariationID(GOOGLE_UPDATE_SERVICE, trial_name,
+                             kDefaultGroupName, trial_base_id);
 
   // Loop starts with group 1 because the field trial automatically creates a
   // default group, which would be group 0.
@@ -49,10 +49,9 @@ void SetupSingleUniformityFieldTrial(
           base::StringPrintf("group_%02d", group_number);
     DVLOG(1) << "    Group name = " << group_name;
     trial->AppendGroup(group_name, kProbabilityPerGroup);
-    chrome_variations::AssociateGoogleVariationID(
-        chrome_variations::GOOGLE_UPDATE_SERVICE, trial_name, group_name,
-        static_cast<chrome_variations::VariationID>(trial_base_id +
-                                                    group_number));
+    AssociateGoogleVariationID(
+        GOOGLE_UPDATE_SERVICE, trial_name, group_name,
+        static_cast<VariationID>(trial_base_id + group_number));
   }
 
   // Now that all groups have been appended, call group() on the trial to
@@ -72,8 +71,7 @@ void SetupNewInstallUniformityTrial(const base::Time install_date) {
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrialList::FactoryGetFieldTrial(
           "UMA-New-Install-Uniformity-Trial", 100, "Disabled",
-          2015, 1, 1, NULL));
-  trial->UseOneTimeRandomization();
+          2015, 1, 1, base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));
   trial->AppendGroup("Control", 50);
   trial->AppendGroup("Experiment", 50);
   const base::Time start_date = base::Time::FromLocalExploded(kStartDate);
@@ -85,8 +83,6 @@ void SetupNewInstallUniformityTrial(const base::Time install_date) {
 
 }  // namespace
 
-namespace chrome_variations {
-
 void SetupUniformityFieldTrials(const base::Time install_date) {
   // One field trial will be created for each entry in this array. The i'th
   // field trial will have |trial_sizes[i]| groups in it, including the default
@@ -96,26 +92,28 @@ void SetupUniformityFieldTrials(const base::Time install_date) {
   // Declare our variation ID bases along side this array so we can loop over it
   // and assign the IDs appropriately. So for example, the 1 percent experiments
   // should have a size of 100 (100/100 = 1).
-  const chrome_variations::VariationID trial_base_ids[] = {
-    chrome_variations::UNIFORMITY_1_PERCENT_BASE,
-    chrome_variations::UNIFORMITY_5_PERCENT_BASE,
-    chrome_variations::UNIFORMITY_10_PERCENT_BASE,
-    chrome_variations::UNIFORMITY_20_PERCENT_BASE,
-    chrome_variations::UNIFORMITY_50_PERCENT_BASE
+  const VariationID trial_base_ids[] = {
+    UNIFORMITY_1_PERCENT_BASE,
+    UNIFORMITY_5_PERCENT_BASE,
+    UNIFORMITY_10_PERCENT_BASE,
+    UNIFORMITY_20_PERCENT_BASE,
+    UNIFORMITY_50_PERCENT_BASE
   };
 
   const std::string kOneTimeRandomizedTrialName =
       "UMA-Uniformity-Trial-%d-Percent";
   for (size_t i = 0; i < arraysize(num_trial_groups); ++i) {
-    SetupSingleUniformityFieldTrial(true, kOneTimeRandomizedTrialName,
+    SetupSingleUniformityFieldTrial(base::FieldTrial::ONE_TIME_RANDOMIZED,
+                                    kOneTimeRandomizedTrialName,
                                     trial_base_ids[i], num_trial_groups[i]);
   }
 
   // Setup a 5% session-randomized uniformity trial.
   const std::string kSessionRandomizedTrialName =
       "UMA-Session-Randomized-Uniformity-Trial-%d-Percent";
-  SetupSingleUniformityFieldTrial(false, kSessionRandomizedTrialName,
-      chrome_variations::UNIFORMITY_SESSION_RANDOMIZED_5_PERCENT_BASE, 20);
+  SetupSingleUniformityFieldTrial(
+      base::FieldTrial::SESSION_RANDOMIZED, kSessionRandomizedTrialName,
+      UNIFORMITY_SESSION_RANDOMIZED_5_PERCENT_BASE, 20);
 
   SetupNewInstallUniformityTrial(install_date);
 }
diff --git a/chrome/common/metrics/variations/variations_util_unittest.cc b/chrome/common/metrics/variations/variations_util_unittest.cc
index 6ad78db..173133a 100644
--- a/chrome/common/metrics/variations/variations_util_unittest.cc
+++ b/chrome/common/metrics/variations/variations_util_unittest.cc
@@ -39,6 +39,18 @@ bool IsFieldTrialActive(const std::string& trial_name) {
   return false;
 }
 
+// Call FieldTrialList::FactoryGetFieldTrial() with a future expiry date.
+scoped_refptr<base::FieldTrial> CreateFieldTrial(
+    const std::string& trial_name,
+    int total_probability,
+    const std::string& default_group_name,
+    int* default_group_number) {
+  return base::FieldTrialList::FactoryGetFieldTrial(
+      trial_name, total_probability, default_group_name,
+      base::FieldTrialList::kNoExpirationYear, 1, 1,
+      base::FieldTrial::SESSION_RANDOMIZED, default_group_number);
+}
+
 }  // namespace
 
 class VariationsUtilTest : public ::testing::Test {
@@ -49,22 +61,11 @@ class VariationsUtilTest : public ::testing::Test {
     ui_thread_.reset(new content::TestBrowserThread(
         content::BrowserThread::UI, &message_loop_));
 
-    base::Time now = base::Time::NowFromSystemTime();
-    base::TimeDelta one_year = base::TimeDelta::FromDays(365);
-    base::Time::Exploded exploded;
-
-    base::Time next_year_time = now + one_year;
-    next_year_time.LocalExplode(&exploded);
-    next_year_ = exploded.year;
-
     // Ensure that the maps are cleared between tests, since they are stored as
     // process singletons.
     testing::ClearAllVariationIDs();
   }
 
- protected:
-  int next_year_;
-
  private:
   base::FieldTrialList field_trial_list_;
   base::MessageLoop message_loop_;
@@ -115,10 +116,7 @@ TEST_F(VariationsUtilTest, GetFieldTrialActiveGroups) {
 TEST_F(VariationsUtilTest, DisableImmediately) {
   int default_group_number = -1;
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial("trial", 100, "default",
-                                                 next_year_, 12, 12,
-                                                 &default_group_number));
-  trial->Disable();
+      CreateFieldTrial("trial", 100, "default", &default_group_number));
 
   ASSERT_EQ(default_group_number, trial->group());
   ASSERT_EQ(EMPTY_ID, GetIDForTrial(GOOGLE_WEB_PROPERTIES, trial.get()));
@@ -132,8 +130,8 @@ TEST_F(VariationsUtilTest, DisableAfterInitialization) {
   const std::string non_default_name = "non_default";
 
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial("trial", 100, default_name,
-                                                 next_year_, 12, 12, NULL));
+      CreateFieldTrial("trial", 100, default_name, NULL));
+
   trial->AppendGroup(non_default_name, 100);
   AssociateGoogleVariationID(GOOGLE_WEB_PROPERTIES, trial->trial_name(),
       default_name, TEST_VALUE_A);
@@ -148,8 +146,7 @@ TEST_F(VariationsUtilTest, DisableAfterInitialization) {
 TEST_F(VariationsUtilTest, AssociateGoogleVariationID) {
   const std::string default_name1 = "default";
   scoped_refptr<base::FieldTrial> trial_true(
-      base::FieldTrialList::FactoryGetFieldTrial("d1", 10, default_name1,
-                                                 next_year_, 12, 31, NULL));
+      CreateFieldTrial("d1", 10, default_name1, NULL));
   const std::string winner = "TheWinner";
   int winner_group = trial_true->AppendGroup(winner, 10);
 
@@ -166,8 +163,7 @@ TEST_F(VariationsUtilTest, AssociateGoogleVariationID) {
 
   const std::string default_name2 = "default2";
   scoped_refptr<base::FieldTrial> trial_false(
-      base::FieldTrialList::FactoryGetFieldTrial("d2", 10, default_name2,
-                                                 next_year_, 12, 31, NULL));
+      CreateFieldTrial("d2", 10, default_name2, NULL));
   const std::string loser = "ALoser";
   const int loser_group = trial_false->AppendGroup(loser, 0);
 
@@ -186,8 +182,8 @@ TEST_F(VariationsUtilTest, AssociateGoogleVariationID) {
 TEST_F(VariationsUtilTest, NoAssociation) {
   const std::string default_name = "default";
   scoped_refptr<base::FieldTrial> no_id_trial(
-      base::FieldTrialList::FactoryGetFieldTrial("d3", 10, default_name,
-                                                 next_year_, 12, 31, NULL));
+      CreateFieldTrial("d3", 10, default_name, NULL));
+
   const std::string winner = "TheWinner";
   const int winner_group = no_id_trial->AppendGroup(winner, 10);
 
@@ -274,8 +270,7 @@ TEST_F(VariationsUtilTest, AssociateVariationParams_DoesntActivateTrial) {
 
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial(kTrialName, 100, "A",
-                                                 next_year_, 1, 1, NULL));
+      CreateFieldTrial(kTrialName, 100, "A", NULL));
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
 
   std::map<std::string, std::string> params;
@@ -309,8 +304,7 @@ TEST_F(VariationsUtilTest, GetVariationParams_ActivatesTrial) {
 
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial(kTrialName, 100, "A",
-                                                 next_year_, 1, 1, NULL));
+      CreateFieldTrial(kTrialName, 100, "A", NULL));
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
 
   std::map<std::string, std::string> params;
@@ -323,8 +317,7 @@ TEST_F(VariationsUtilTest, GetVariationParamValue_ActivatesTrial) {
 
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
   scoped_refptr<base::FieldTrial> trial(
-      base::FieldTrialList::FactoryGetFieldTrial(kTrialName, 100, "A",
-                                                 next_year_, 1, 1, NULL));
+      CreateFieldTrial(kTrialName, 100, "A", NULL));
   ASSERT_FALSE(IsFieldTrialActive(kTrialName));
 
   std::map<std::string, std::string> params;
@@ -391,9 +384,7 @@ TEST_F(VariationsUtilTest, CollectionsCoexist) {
   const std::string default_name = "default";
   int default_group_number = -1;
   scoped_refptr<base::FieldTrial> trial_true(
-      base::FieldTrialList::FactoryGetFieldTrial("d1", 10, default_name,
-                                                 next_year_, 12, 31,
-                                                 &default_group_number));
+      CreateFieldTrial("d1", 10, default_name, &default_group_number));
   ASSERT_EQ(default_group_number, trial_true->group());
   ASSERT_EQ(default_name, trial_true->group_name());