Use low entropy for studies that send experiment IDs to Google properties.

components/variations/variations_seed_processor.h

 // Copyright 2013 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.
 
 #ifndef COMPONENTS_VARIATIONS_VARIATIONS_SEED_PROCESSOR_H_
 #define COMPONENTS_VARIATIONS_VARIATIONS_SEED_PROCESSOR_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 21 matching lines @@
 // Helper class to instantiate field trials from a variations seed.
 class VariationsSeedProcessor {
  public:
   typedef base::Callback<void(uint32_t, const base::string16&)>
       UIStringOverrideCallback;
 
   VariationsSeedProcessor();
   virtual ~VariationsSeedProcessor();
 
   // Creates field trials from the specified variations |seed|, based on the
-  // specified configuration, as specified in the parameters.
-  void CreateTrialsFromSeed(const VariationsSeed& seed,
-                            const std::string& locale,
-                            const base::Time& reference_date,
-                            const base::Version& version,
-                            Study_Channel channel,
-                            Study_FormFactor form_factor,
-                            const std::string& hardware_class,
-                            const std::string& session_consistency_country,
-                            const std::string& permanent_consistency_country,
-                            const UIStringOverrideCallback& override_callback,
-                            base::FeatureList* feature_list);
+  // specified configuration, as specified in the parameters. Any study that
+  // should use low entropy will use |low_entropy_provider| for group
+  // selection. These studies are defined by ShouldStudyUseLowEntropy;
+  void CreateTrialsFromSeed(
+      const VariationsSeed& seed,
+      const std::string& locale,
+      const base::Time& reference_date,
+      const base::Version& version,
+      Study_Channel channel,
+      Study_FormFactor form_factor,
+      const std::string& hardware_class,
+      const std::string& session_consistency_country,
+      const std::string& permanent_consistency_country,
+      const UIStringOverrideCallback& override_callback,
+      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
+  // study that can send data to other Google properties.
+  static bool ShouldStudyUseLowEntropy(const Study& study);
 
  private:
   friend class VariationsSeedProcessorTest;
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            AllowForceGroupAndVariationId);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            AllowVariationIdWithForcingFlag);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            ForbidForceGroupWithVariationId);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest, ForceGroupWithFlag1);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest, ForceGroupWithFlag2);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            ForceGroup_ChooseFirstGroupWithFlag);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            ForceGroup_DontChooseGroupWithFlag);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest, IsStudyExpired);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest, VariationParams);
   FRIEND_TEST_ALL_PREFIXES(VariationsSeedProcessorTest,
                            VariationParamsWithForcingFlag);
 
   // Check if the |study| is only associated with platform Android/iOS and
   // channel dev/canary. If so, forcing flag and variation id can both be set.
   // (Otherwise, forcing_flag and variation_id are mutually exclusive.)
   bool AllowVariationIdWithForcingFlag(const Study& study);
 
   // Creates and registers a field trial from the |processed_study| data.
-  // Disables the trial if |processed_study.is_expired| is true.
-  void CreateTrialFromStudy(const ProcessedStudy& processed_study,
-                            const UIStringOverrideCallback& override_callback,
-                            base::FeatureList* feature_list);
+  // Disables the trial if |processed_study.is_expired| is true. Uses
+  // |low_entropy_provider| if ShouldStudyUseLowEntropy returns true for the
+  // study.
+  void CreateTrialFromStudy(
+      const ProcessedStudy& processed_study,
+      const UIStringOverrideCallback& override_callback,
+      const base::FieldTrial::EntropyProvider* low_entropy_provider,
+      base::FeatureList* feature_list);
 
   DISALLOW_COPY_AND_ASSIGN(VariationsSeedProcessor);
 };
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_SEED_PROCESSOR_H_