Implement plumbing for variations in feedback reports.

components/variations/variations_http_header_provider.h

 // Copyright 2014 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_HTTP_HEADER_PROVIDER_H_
 #define COMPONENTS_VARIATIONS_VARIATIONS_HTTP_HEADER_PROVIDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 17 matching lines @@
 // This class is a thread-safe singleton.
 class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
                                      public SyntheticTrialObserver {
  public:
   static VariationsHttpHeaderProvider* GetInstance();
 
   // Returns the value of the client data header, computing and caching it if
   // necessary.
   std::string GetClientDataHeader();
 
+  // Returns a space-separated string containing the list of current active
+  // variations (as would be reported in the |variation_id| repeated field of
+  // the ClientVariations proto). The returned string is guaranteed to have a
+  // a leading and trailing space, e.g. " 123 234 345 ".
+  std::string GetVariationsString();
+
   // Sets *additional* variation ids and trigger variation ids to be encoded in
   // the X-Client-Data request header.  This is intended for development use to
   // force a server side experiment id.  |variation_ids| should be a
   // comma-separated string of numeric experiment ids.  If an id is prefixed
   // with "t" it will be treated as a trigger experiment id.
   bool SetDefaultVariationIds(const std::string& variation_ids);
 
   // Resets any cached state for tests.
   void ResetForTesting();
 
  private:
   friend struct base::DefaultSingletonTraits<VariationsHttpHeaderProvider>;
 
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            SetDefaultVariationIds_Valid);
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            SetDefaultVariationIds_Invalid);
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            OnFieldTrialGroupFinalized);
+  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
+                           GetVariationsString);
 
   VariationsHttpHeaderProvider();
   ~VariationsHttpHeaderProvider() override;
 
   // base::FieldTrialList::Observer:
   // This will add the variation ID associated with |trial_name| and
   // |group_name| to the variation ID cache.
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override;
 
   // metrics::SyntheticTrialObserver:
   void OnSyntheticTrialsChanged(
       const std::vector<SyntheticTrialGroup>& groups) override;
 
   // Prepares the variation IDs cache with initial values if not already done.
   // This method also registers the caller with the FieldTrialList to receive
   // new variation IDs.
   void InitVariationIDsCacheIfNeeded();
 
   // Takes whatever is currently in |variation_ids_set_| and recreates
   // |variation_ids_header_| with it.  Assumes the the |lock_| is currently
   // held.
   void UpdateVariationIDsHeaderValue();
 
+  // Returns the currently active set of variation ids, which includes any
+  // default values, synthetic variations and actual field trial variations.
+  std::set<VariationID> GetAllVariationIds();
+
   // Guards |variation_ids_cache_initialized_|, |variation_ids_set_| and
   // |variation_ids_header_|.
   base::Lock lock_;
 
   // Whether or not we've initialized the cache.
   bool variation_ids_cache_initialized_;
 
   // Keep a cache of variation IDs that are transmitted in headers to Google.
   // This consists of a list of valid IDs, and the actual transmitted header.
   std::set<VariationID> variation_ids_set_;
   std::set<VariationID> variation_trigger_ids_set_;
 
   // Provides the google experiment ids forced from command line.
   std::set<VariationID> default_variation_ids_set_;
   std::set<VariationID> default_trigger_id_set_;
 
   // Variations ids from synthetic field trials.
   std::set<VariationID> synthetic_variation_ids_set_;
 
   std::string variation_ids_header_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsHttpHeaderProvider);
 };
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_HTTP_HEADER_PROVIDER_H_