Restoring the chrome variatioons client, with a fix for browser_test failures caused by it.

chrome/browser/metrics/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 CHROME_BROWSER_METRICS_VARIATIONS_SERVICE_H_
+#define CHROME_BROWSER_METRICS_VARIATIONS_SERVICE_H_
+#pragma once
+
+#include <string>
+
+#include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
+#include "base/time.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/metrics/proto/study.pb.h"
+#include "chrome/browser/metrics/proto/trials_seed.pb.h"
+#include "chrome/common/chrome_version_info.h"
+#include "content/public/common/url_fetcher_delegate.h"
+
+class PrefService;
+
+// Used to setup field trials based on stored variations seed data, and fetch
+// new seed data from the variations server.
+class VariationsService : public content::URLFetcherDelegate {
+ public:
+  VariationsService();
+  virtual ~VariationsService();
+
+  // Creates field trials based on Variations Seed loaded from local prefs. If
+  // there is a problem loading the seed data, all trials specified by the seed
+  // may not be created.
+  bool CreateTrialsFromSeed(PrefService* local_prefs);
+
+  // Starts the fetching process, where |OnURLFetchComplete| is called with the
+  // response.
+  void StartFetchingVariationsSeed();
+
+  // content::URLFetcherDelegate implementation:
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
+  // Register Variations related prefs in Local State.
+  static void RegisterPrefs(PrefService* prefs);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyChannel);
+  FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyVersion);
+  FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyVersionWildcards);
+  FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyDate);
+
+  // Store the given seed data to the given local prefs. Note that |seed_data|
+  // is assumed to be the raw serialized protobuf data stored in a string. It
+  // will be Base64Encoded for storage. If the string is invalid or the encoding
+  // fails, the |local_prefs| is left as is.
+  void StoreSeedData(const std::string& seed_data, PrefService* local_prefs);
+
+  // Returns whether |study| should be added to the local field trials list
+  // according to its restriction parameters.
+  static bool ShouldAddStudy(const chrome_variations::Study& study);
+
+  // Checks whether |study| is applicable for the given |channel|.
+  static bool CheckStudyChannel(const chrome_variations::Study& study,
+                                chrome::VersionInfo::Channel channel);
+
+  // Checks whether |study| is applicable for the given version string.
+  static bool CheckStudyVersion(const chrome_variations::Study& study,
+                                const std::string& version_string);
+
+  // Checks whether |study| is applicable for the given date/time.
+  static bool CheckStudyDate(const chrome_variations::Study& study,
+                             const base::Time& date_time);
+
+  // Loads the Variations seed data from the given local prefs into |seed|. If
+  // there is a problem with loading, the pref value is cleared and false is
+  // returned. If successful, |seed| will contain the loaded data and true is
+  // returned.
+  bool LoadTrialsSeedFromPref(PrefService* local_prefs,
+                              chrome_variations::TrialsSeed* seed);
+
+  void CreateTrialFromStudy(const chrome_variations::Study& study);
+
+  // Contains the current seed request. Will only have a value while a request
+  // is pending, and will be reset by |OnURLFetchComplete|.
+  scoped_ptr<content::URLFetcher> pending_seed_request_;
+
+  // The variations seed data being used for this session.
+  // TODO(jwd): This should be removed. When the seed data is loaded, it will be
+  // used immediately so it won't need to be stored.
+  chrome_variations::TrialsSeed variations_seed_;
+};
+
+#endif  // CHROME_BROWSER_METRICS_VARIATIONS_SERVICE_H_