Propagate entropy value to VariationsIdsProvider

The values are passed from the VariationsService to the
VariationsIdsProvider. This is needed to include the
low_entropy_source_value in the X-Client-Data header.

Change-Id: I81141eb22396c31c05101229b900631bd0a9a5b8
Bug: 1134444
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444137Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Karthika Pai <karthikapai@google.com>
Cr-Commit-Position: refs/heads/master@{#814975}

android_webview/browser/aw_feature_list_creator.cc

@@ -216,14 +216,16 @@ void AwFeatureListCreator::SetUpFieldTrials() {
 
   // Populate FieldTrialList. Since low_entropy_provider is null, it will fall
   // back to the provider we previously gave to FieldTrialList, which is a low
-  // entropy provider.
+  // entropy provider. The X-Client-Data header is not reported on WebView, so
+  // we pass an empty object as the |low_entropy_source_value|.
   variations_field_trial_creator_->SetupFieldTrials(
       cc::switches::kEnableGpuBenchmarking, switches::kEnableFeatures,
       switches::kDisableFeatures, std::vector<std::string>(),
       content::GetSwitchDependentFeatureOverrides(
           *base::CommandLine::ForCurrentProcess()),
       /*low_entropy_provider=*/nullptr, std::make_unique<base::FeatureList>(),
-      aw_field_trials_.get(), &ignored_safe_seed_manager);
+      aw_field_trials_.get(), &ignored_safe_seed_manager,
+      /*low_entropy_source_value=*/base::nullopt);
 }
 
 void AwFeatureListCreator::CreateLocalState() {

components/metrics/metrics_state_manager.cc

@@ -216,6 +216,10 @@ int64_t MetricsStateManager::GetInstallDate() const {
   return ReadInstallDate(local_state_);
 }
 
+int MetricsStateManager::GetLowEntropySource() {
+  return entropy_state_.GetLowEntropySource();
+}
+
 void MetricsStateManager::ForceClientIdCreation() {
   // TODO(asvitkine): Ideally, all tests would actually set up consent properly,
   // so the command-line check wouldn't be needed here.
@@ -375,10 +379,6 @@ std::string MetricsStateManager::GetHighEntropySource() {
   return entropy_state_.GetHighEntropySource(initial_client_id_);
 }
 
-int MetricsStateManager::GetLowEntropySource() {
-  return entropy_state_.GetLowEntropySource();
-}
-
 int MetricsStateManager::GetOldLowEntropySource() {
   return entropy_state_.GetOldLowEntropySource();
 }

components/metrics/metrics_state_manager.h

@@ -57,6 +57,9 @@ class MetricsStateManager final {
   // not opted in to metrics reporting.
   const std::string& client_id() const { return client_id_; }
 
+  // Returns the low entropy source for this client.
+  int GetLowEntropySource();
+
   // The CleanExitBeacon, used to determine whether the previous Chrome browser
   // session terminated gracefully.
   CleanExitBeacon* clean_exit_beacon() { return &clean_exit_beacon_; }
@@ -153,9 +156,6 @@ class MetricsStateManager final {
   // |provisional_client_id_| must be set before calling this.
   std::string GetHighEntropySource();
 
-  // Returns the low entropy source for this client.
-  int GetLowEntropySource();
-
   // Returns the old low entropy source for this client.
   int GetOldLowEntropySource();
 

components/variations/service/variations_field_trial_creator.cc

@@ -432,7 +432,8 @@ bool VariationsFieldTrialCreator::SetupFieldTrials(
         low_entropy_provider,
     std::unique_ptr<base::FeatureList> feature_list,
     PlatformFieldTrials* platform_field_trials,
-    SafeSeedManager* safe_seed_manager) {
+    SafeSeedManager* safe_seed_manager,
+    base::Optional<int> low_entropy_source_value) {
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableBenchmarking) ||
@@ -468,11 +469,13 @@ bool VariationsFieldTrialCreator::SetupFieldTrials(
 
   VariationsIdsProvider* http_header_provider =
       VariationsIdsProvider::GetInstance();
+  http_header_provider->SetLowEntropySourceValue(low_entropy_source_value);
   // Force the variation ids selected in chrome://flags and/or specified using
   // the command-line flag.
   auto result = http_header_provider->ForceVariationIds(
       variation_ids,
       command_line->GetSwitchValueASCII(switches::kForceVariationIds));
+
   switch (result) {
     case VariationsIdsProvider::ForceIdsResult::INVALID_SWITCH_ENTRY:
       ExitWithMessage(base::StringPrintf("Invalid --%s list specified.",

components/variations/service/variations_field_trial_creator.h

@@ -70,6 +70,8 @@ class VariationsFieldTrialCreator {
   // |safe_seed_manager| should be notified of the combined server and client
   // state that was activated to create the field trials (only when the return
   // value is true).
+  // |low_entropy_source_value| contains the low entropy source value that was
+  // used for client-side randomization of variations.
   // |extra_overrides| gives a list of feature overrides that should be applied
   // after the features explicitly disabled/enabled from the command line via
   // --disable-features and --enable-features, but before field trials.
@@ -88,7 +90,8 @@ class VariationsFieldTrialCreator {
           low_entropy_provider,
       std::unique_ptr<base::FeatureList> feature_list,
       PlatformFieldTrials* platform_field_trials,
-      SafeSeedManager* safe_seed_manager);
+      SafeSeedManager* safe_seed_manager,
+      base::Optional<int> low_entropy_source_value);
 
   // Returns all of the client state used for filtering studies.
   // As a side-effect, may update the stored permanent consistency country.

components/variations/service/variations_field_trial_creator_unittest.cc

@@ -249,7 +249,7 @@ class TestVariationsFieldTrialCreator : public VariationsFieldTrialCreator {
         "", "", "", std::vector<std::string>(),
         std::vector<base::FeatureList::FeatureOverrideInfo>(), nullptr,
         std::make_unique<base::FeatureList>(), &platform_field_trials,
-        safe_seed_manager_);
+        safe_seed_manager_, base::nullopt);
   }
 
   TestVariationsSeedStore* seed_store() { return &seed_store_; }
@@ -500,7 +500,7 @@ TEST_F(FieldTrialCreatorTest, SetupFieldTrials_LoadsCountryOnFirstRun) {
       "", "", "", std::vector<std::string>(),
       std::vector<base::FeatureList::FeatureOverrideInfo>(), nullptr,
       std::make_unique<base::FeatureList>(), &platform_field_trials,
-      &safe_seed_manager));
+      &safe_seed_manager, base::nullopt));
 
   EXPECT_EQ(kTestSeedExperimentName,
             base::FieldTrialList::FindFullName(kTestSeedStudyName));

components/variations/service/variations_service.cc

@@ -999,7 +999,8 @@ bool VariationsService::SetupFieldTrials(
   return field_trial_creator_.SetupFieldTrials(
       kEnableGpuBenchmarking, kEnableFeatures, kDisableFeatures, variation_ids,
       extra_overrides, CreateLowEntropyProvider(), std::move(feature_list),
-      platform_field_trials, &safe_seed_manager_);
+      platform_field_trials, &safe_seed_manager_,
+      state_manager_->GetLowEntropySource());
 }
 
 void VariationsService::OverrideCachedUIStrings() {

components/variations/variations_ids_provider.cc

@@ -110,6 +110,18 @@ VariationsIdsProvider::GetVariationsVectorForWebPropertiesKeys() {
   return GetVariationsVectorImpl(web_properties_keys);
 }
 
+void VariationsIdsProvider::SetLowEntropySourceValue(
+    base::Optional<int> low_entropy_source_value) {
+  // The low entropy source value is an integer that is between 0 and 7999,
+  // inclusive. See components/metrics/metrics_state_manager.cc for the logic to
+  // generate it.
+  if (low_entropy_source_value) {
+    DCHECK(low_entropy_source_value.value() >= 0 &&
+           low_entropy_source_value.value() <= 7999);
+  }
+  low_entropy_source_value_ = low_entropy_source_value;
+}
+
 VariationsIdsProvider::ForceIdsResult VariationsIdsProvider::ForceVariationIds(
     const std::vector<std::string>& variation_ids,
     const std::string& command_line_variation_ids) {

components/variations/variations_ids_provider.h

@@ -96,6 +96,10 @@ class VariationsIdsProvider : public base::FieldTrialList::Observer,
   // related keys.
   std::vector<VariationID> GetVariationsVectorForWebPropertiesKeys();
 
+  // Sets low entropy source value that was used for client-side randomization
+  // of variations.
+  void SetLowEntropySourceValue(base::Optional<int> low_entropy_source_value);
+
   // Result of ForceVariationIds() call.
   enum class ForceIdsResult {
     SUCCESS,
@@ -218,6 +222,10 @@ class VariationsIdsProvider : public base::FieldTrialList::Observer,
   // Guards access to variables below.
   base::Lock lock_;
 
+  // Low entropy source value from client that was used for client-side
+  // randomization of variations.
+  base::Optional<int> low_entropy_source_value_;
+
   // Whether or not we've initialized the caches.
   bool variation_ids_cache_initialized_;