[ios] Pass FieldTrial::EntropyProvider Pointer into CreateTrialsFromSeed

Now that |low_entropy_provider| is used later in
VariationsFieldTrialCreator::SetupFieldTrials(),
VariationsFieldTrialCreator::CreateTrialsFromSeed() shouldn't
own |low_entropy_provider|.

Bug: 1138603
Change-Id: I53ba8d2b7160bd3c9f02e92af4bd53ca72c63f25
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2525856
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826023}

components/variations/service/variations_field_trial_creator.cc

@@ -163,8 +163,7 @@ std::string VariationsFieldTrialCreator::GetLatestCountry() const {
 }
 
 bool VariationsFieldTrialCreator::CreateTrialsFromSeed(
-    std::unique_ptr<const base::FieldTrial::EntropyProvider>
-        low_entropy_provider,
+    const base::FieldTrial::EntropyProvider& low_entropy_provider,
     base::FeatureList* feature_list,
     SafeSeedManager* safe_seed_manager) {
   TRACE_EVENT0("startup", "VariationsFieldTrialCreator::CreateTrialsFromSeed");
@@ -206,7 +205,7 @@ bool VariationsFieldTrialCreator::CreateTrialsFromSeed(
       seed, *client_filterable_state,
       base::BindRepeating(&VariationsFieldTrialCreator::OverrideUIString,
                           base::Unretained(this)),
-      low_entropy_provider.get(), feature_list);
+      low_entropy_provider, feature_list);
 
   // Store into the |safe_seed_manager| the combined server and client data used
   // to create the field trials. But, as an optimization, skip this step when
@@ -522,16 +521,14 @@ bool VariationsFieldTrialCreator::SetupFieldTrials(
     used_testing_config = true;
   }
 #endif  // BUILDFLAG(FIELDTRIAL_TESTING_ENABLED)
-  const base::FieldTrial::EntropyProvider& low_entry_provider_ref =
-      *low_entropy_provider.get();
   bool used_seed = false;
   if (!used_testing_config) {
-    used_seed = CreateTrialsFromSeed(std::move(low_entropy_provider),
-                                     feature_list.get(), safe_seed_manager);
+    used_seed = CreateTrialsFromSeed(*low_entropy_provider, feature_list.get(),
+                                     safe_seed_manager);
   }
 
   platform_field_trials->SetupFeatureControllingFieldTrials(
-      used_seed, low_entry_provider_ref, feature_list.get());
+      used_seed, *low_entropy_provider, feature_list.get());
 
   base::FeatureList::SetInstance(std::move(feature_list));
 

components/variations/service/variations_field_trial_creator.h

@@ -154,8 +154,7 @@ class VariationsFieldTrialCreator {
   // successfully; and if so, stores the loaded variations state into the
   // |safe_seed_manager|.
   bool CreateTrialsFromSeed(
-      std::unique_ptr<const base::FieldTrial::EntropyProvider>
-          low_entropy_provider,
+      const base::FieldTrial::EntropyProvider& low_entropy_provider,
       base::FeatureList* feature_list,
       SafeSeedManager* safe_seed_manager);
 

components/variations/variations_seed_processor.cc

@@ -197,7 +197,7 @@ void VariationsSeedProcessor::CreateTrialsFromSeed(
     const VariationsSeed& seed,
     const ClientFilterableState& client_state,
     const UIStringOverrideCallback& override_callback,
-    const base::FieldTrial::EntropyProvider* low_entropy_provider,
+    const base::FieldTrial::EntropyProvider& low_entropy_provider,
     base::FeatureList* feature_list) {
   std::vector<ProcessedStudy> filtered_studies;
   FilterAndValidateStudies(seed, client_state, &filtered_studies);
@@ -225,7 +225,7 @@ bool VariationsSeedProcessor::ShouldStudyUseLowEntropy(const Study& study) {
 void VariationsSeedProcessor::CreateTrialFromStudy(
     const ProcessedStudy& processed_study,
     const UIStringOverrideCallback& override_callback,
-    const base::FieldTrial::EntropyProvider* low_entropy_provider,
+    const base::FieldTrial::EntropyProvider& low_entropy_provider,
     base::FeatureList* feature_list) {
   const Study& study = *processed_study.study();
 
@@ -290,7 +290,7 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
           study.name(), processed_study.total_probability(),
           processed_study.GetDefaultExperimentName(), randomization_type,
           randomization_seed, nullptr,
-          ShouldStudyUseLowEntropy(study) ? low_entropy_provider : nullptr));
+          ShouldStudyUseLowEntropy(study) ? &low_entropy_provider : nullptr));
 
   bool has_overrides = false;
   bool enables_or_disables_features = false;

components/variations/variations_seed_processor.h

@@ -47,7 +47,7 @@ class VariationsSeedProcessor {
       const VariationsSeed& seed,
       const ClientFilterableState& client_state,
       const UIStringOverrideCallback& override_callback,
-      const base::FieldTrial::EntropyProvider* low_entropy_provider,
+      const base::FieldTrial::EntropyProvider& low_entropy_provider,
       base::FeatureList* feature_list);
 
   // If the given |study| should alwoys use low entropy. This is true for any
@@ -85,7 +85,7 @@ class VariationsSeedProcessor {
   void CreateTrialFromStudy(
       const ProcessedStudy& processed_study,
       const UIStringOverrideCallback& override_callback,
-      const base::FieldTrial::EntropyProvider* low_entropy_provider,
+      const base::FieldTrial::EntropyProvider& low_entropy_provider,
       base::FeatureList* feature_list);
 
   DISALLOW_COPY_AND_ASSIGN(VariationsSeedProcessor);

components/variations/variations_seed_processor_unittest.cc

@@ -129,26 +129,28 @@ class VariationsSeedProcessorTest : public ::testing::Test {
   }
 
   bool CreateTrialFromStudy(const Study& study) {
+    base::MockEntropyProvider mock_low_entropy_provider(0.9);
     return CreateTrialFromStudyWithFeatureListAndEntropyOverride(
-        study, nullptr, base::FeatureList::GetInstance());
+        study, mock_low_entropy_provider, base::FeatureList::GetInstance());
   }
 
   bool CreateTrialFromStudyWithEntropyOverride(
       const Study& study,
-      const base::FieldTrial::EntropyProvider* override_entropy_provider) {
+      const base::FieldTrial::EntropyProvider& override_entropy_provider) {
     return CreateTrialFromStudyWithFeatureListAndEntropyOverride(
         study, override_entropy_provider, base::FeatureList::GetInstance());
   }
 
   bool CreateTrialFromStudyWithFeatureList(const Study& study,
                                            base::FeatureList* feature_list) {
-    return CreateTrialFromStudyWithFeatureListAndEntropyOverride(study, nullptr,
-                                                                 feature_list);
+    base::MockEntropyProvider mock_low_entropy_provider(0.9);
+    return CreateTrialFromStudyWithFeatureListAndEntropyOverride(
+        study, mock_low_entropy_provider, feature_list);
   }
 
   bool CreateTrialFromStudyWithFeatureListAndEntropyOverride(
       const Study& study,
-      const base::FieldTrial::EntropyProvider* override_entropy_provider,
+      const base::FieldTrial::EntropyProvider& override_entropy_provider,
       base::FeatureList* feature_list) {
     ProcessedStudy processed_study;
     const bool is_expired = internal::IsStudyExpired(study, base::Time::Now());
@@ -289,9 +291,10 @@ TEST_F(VariationsSeedProcessorTest,
 
     base::FeatureList feature_list;
     study1->set_expiry_date(TimeToProtoTime(year_ago));
-    seed_processor.CreateTrialsFromSeed(seed, client_state,
-                                        override_callback_.callback(), nullptr,
-                                        &feature_list);
+    base::MockEntropyProvider mock_low_entropy_provider(0.9);
+    seed_processor.CreateTrialsFromSeed(
+        seed, client_state, override_callback_.callback(),
+        mock_low_entropy_provider, &feature_list);
     EXPECT_EQ(kGroup1Name, base::FieldTrialList::FindFullName(kTrialName));
   }
 
@@ -304,9 +307,10 @@ TEST_F(VariationsSeedProcessorTest,
     base::FeatureList feature_list;
     study1->clear_expiry_date();
     study2->set_expiry_date(TimeToProtoTime(year_ago));
-    seed_processor.CreateTrialsFromSeed(seed, client_state,
-                                        override_callback_.callback(), nullptr,
-                                        &feature_list);
+    base::MockEntropyProvider mock_low_entropy_provider(0.9);
+    seed_processor.CreateTrialsFromSeed(
+        seed, client_state, override_callback_.callback(),
+        mock_low_entropy_provider, &feature_list);
     EXPECT_EQ(kGroup1Name, base::FieldTrialList::FindFullName(kTrialName));
   }
 }
@@ -560,9 +564,10 @@ TEST_F(VariationsSeedProcessorTest, StartsActive) {
   client_state.platform = Study::PLATFORM_ANDROID;
 
   VariationsSeedProcessor seed_processor;
-  seed_processor.CreateTrialsFromSeed(seed, client_state,
-                                      override_callback_.callback(), nullptr,
-                                      base::FeatureList::GetInstance());
+  base::MockEntropyProvider mock_low_entropy_provider(0.9);
+  seed_processor.CreateTrialsFromSeed(
+      seed, client_state, override_callback_.callback(),
+      mock_low_entropy_provider, base::FeatureList::GetInstance());
 
   // Non-specified and ACTIVATE_ON_QUERY should not start active, but
   // ACTIVATE_ON_STARTUP should.
@@ -979,9 +984,9 @@ TEST_F(VariationsSeedProcessorTest, LowEntropyStudyTest) {
   base::MockEntropyProvider mock_low_entropy_provider(0.9);
 
   EXPECT_TRUE(CreateTrialFromStudyWithEntropyOverride(
-      *study1, &mock_low_entropy_provider));
+      *study1, mock_low_entropy_provider));
   EXPECT_TRUE(CreateTrialFromStudyWithEntropyOverride(
-      *study2, &mock_low_entropy_provider));
+      *study2, mock_low_entropy_provider));
 
   // Since no experiment in study1 sends experiment IDs, it will use the high
   // entropy provider, which selects the non-default group.