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

components/variations/service/variations_service.h

 // Copyright (c) 2012 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_SERVICE_VARIATIONS_SERVICE_H_
 #define COMPONENTS_VARIATIONS_SERVICE_VARIATIONS_SERVICE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 160 matching lines @@
 
   // Stores the seed to prefs. Set as virtual and protected so that it can be
   // overridden by tests.
   virtual bool StoreSeed(const std::string& seed_data,
                          const std::string& seed_signature,
                          const std::string& country_code,
                          const base::Time& date_fetched,
                          bool is_delta_compressed,
                          bool is_gzip_compressed);
 
+  // Create an entropy provider based on low entropy. This is used to create
+  // trials for studies that should only depend on low entropy, such as studies
+  // that send experiment IDs to Google web properties. Exposed for testing.

[Alexei Svitkine (slow), 2016/05/18 15:03:30]

Nit: "Exposed for testing." -> "Virtual for testing."

[jwd, 2016/05/18 18:31:41]

Done.

+  virtual std::unique_ptr<const base::FieldTrial::EntropyProvider>
+  CreateLowEntropyProvider();
+
   // Creates the VariationsService with the given |local_state| prefs service
   // and |state_manager|. Does not take ownership of |state_manager|. Caller
   // should ensure that |state_manager| is valid for the lifetime of this class.
   // Use the |Create| factory method to create a VariationsService.
   VariationsService(
       std::unique_ptr<VariationsServiceClient> client,
       std::unique_ptr<web_resource::ResourceRequestAllowedNotifier> notifier,
       PrefService* local_state,
       metrics::MetricsStateManager* state_manager,
       const UIStringOverrider& ui_string_overrider);
@@ skipping 134 matching lines @@
   base::ThreadChecker thread_checker_;
 
   base::WeakPtrFactory<VariationsService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsService);
 };
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_SERVICE_VARIATIONS_SERVICE_H_