Refactor VariationsHttpHeaderProvider.

components/variations/net/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_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_
-#define COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_
-
-#include <set>
-#include <string>
-#include <vector>
-
-#include "base/basictypes.h"
-#include "base/gtest_prod_util.h"
-#include "base/metrics/field_trial.h"
-#include "base/synchronization/lock.h"
-#include "components/metrics/metrics_service.h"
-#include "components/variations/variations_associated_data.h"
-
-namespace content {
-class ResourceContext;
-}
-
-namespace net {
-class HttpRequestHeaders;
-}
-
-class GURL;
-
-namespace base {
-template <typename T> struct DefaultSingletonTraits;
-}
-
-namespace variations {
-
-// A helper class for maintaining client experiments and metrics state
-// transmitted in custom HTTP request headers.
-// This class is a thread-safe singleton.
-class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
-                                     public metrics::SyntheticTrialObserver {
- public:
-  static VariationsHttpHeaderProvider* GetInstance();
-
-  // Adds Chrome experiment and metrics state as custom headers to |headers|.
-  // Some headers may not be set given the |incognito| mode or whether
-  // the user has |uma_enabled|.  Also, we never transmit headers to non-Google
-  // sites, which is checked based on the destination |url|.
-  void AppendHeaders(const GURL& url,
-                     bool incognito,
-                     bool uma_enabled,
-                     net::HttpRequestHeaders* headers);
-
-  // 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);
-
-  // Returns the HTTP header names which are added in this class.
-  std::set<std::string> GetVariationHeaderNames() const;
-
-  // Resets any cached state for tests.
-  void ResetForTesting();
-
- private:
-  friend struct base::DefaultSingletonTraits<VariationsHttpHeaderProvider>;
-
-  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
-                           ShouldAppendHeaders);
-  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
-                           SetDefaultVariationIds_Valid);
-  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
-                           SetDefaultVariationIds_Invalid);
-  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
-                           OnFieldTrialGroupFinalized);
-
-  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<metrics::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();
-
-  // Checks whether variation headers should be appended to requests to the
-  // specified |url|. Returns true for google.<TLD> and youtube.<TLD> URLs.
-  static bool ShouldAppendHeaders(const GURL& url);
-
-  // 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_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_