Retrieving Chrome Variations seed from server and storing in local prefs. Loading seed data from lo…

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 "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/metrics/proto/trials_seed.pb.h"
+#include "content/public/common/url_fetcher_delegate.h"
+
+template <typename T> struct DefaultSingletonTraits;
+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:
+  // Returns the singleton instance;
+  static VariationsService* GetInstance();
+
+  // Loads the Variations seed data from the given local prefs. If there is a
+  // problem with loading, the pref value is cleared.
+  void LoadVariationsSeed(PrefService* local_prefs);
+
+  // Starts the fetching process, where |OnURLFetchComplete| is called with the
+  // response.
+  void StartFetchingVariationsSeed();
+
+  // content::URLFetcherDelegate implementation:
+  virtual void OnURLFetchComplete(const content::URLFetcher* source) OVERRIDE;
+
+  // Register Variations related prefs in Local State.
+  static void RegisterPrefs(PrefService* prefs);
+
+ private:
+  friend struct DefaultSingletonTraits<VariationsService>;
+
+  VariationsService();
+  virtual ~VariationsService();
+
+  // 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);
+
+  // 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_