Have the VariationsService attempt to fetch the seed when an update is ready.

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_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/time.h"
 #include "base/timer.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/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 #include "googleurl/src/gurl.h"
 #include "net/url_request/url_fetcher_delegate.h"
 
 class PrefService;
 
 namespace net {
 class URLFetcher;
 }  // namespace net
 
 namespace chrome_variations {
 
 // Used to setup field trials based on stored variations seed data, and fetch
 // new seed data from the variations server.
-class VariationsService : public net::URLFetcherDelegate {
+class VariationsService : public net::URLFetcherDelegate,
+                          public content::NotificationObserver {
  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);
 
   // Calls FetchVariationsSeed once and repeats this periodically. See
   // implementation for details on the period.
   void StartRepeatedVariationsSeedFetch();
 
-  // Starts the fetching process once, where |OnURLFetchComplete| is called with
-  // the response.
-  void FetchVariationsSeed();
-
-  // net::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, CheckStudyLocale);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyPlatform);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyVersion);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyVersionWildcards);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyStartDate);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, IsStudyExpired);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, LoadSeed);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, StoreSeed);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, ValidateStudy);
 
+  // Overridden from content::NotificationObserver:
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // Starts the fetching process once, where |OnURLFetchComplete| is called with
+  // the response.
+  void FetchVariationsSeed();

[Alexei Svitkine (slow), 2012/07/23 20:26:05]

Nit: Move this below OnURLFetchComplete() so that the virtual implementations
are together.

[Alexei Svitkine (slow), 2012/07/23 20:27:53]

Oops, this comment was from earlier that I hadn't sent out. Ignore it as its no
longer relevant.

+
+  // net::URLFetcherDelegate implementation:

[Alexei Svitkine (slow), 2012/07/23 20:26:05]

Nit: Change this comment to the same style as the one for Observe().

[Alexei Svitkine (slow), 2012/07/23 20:27:53]

Oops, this comment got duplicated since I had it saved from earlier.

+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
   // 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 and the function returns false.
   bool StoreSeedData(const std::string& seed_data,
                      const base::Time& seed_date,
                      PrefService* local_prefs);
 
   // Returns whether |study| should be disabled according to its restriction
   // parameters. Uses |version_info| for min / max version checks and
@@ skipping 46 matching lines @@
   // is pending, and will be reset by |OnURLFetchComplete|.
   scoped_ptr<net::URLFetcher> pending_seed_request_;
 
   // The URL to use for querying the variations server.
   GURL variations_server_url_;
 
   // The timer used to repeatedly ping the server. Keep this as an instance
   // member so if VariationsService goes out of scope, the timer is
   // automatically cancelled.
   base::RepeatingTimer<VariationsService> timer_;
+
+  // The registrar used to manage our Notification registrations.
+  content::NotificationRegistrar registrar_;
 };
 
 }  // namespace chrome_variations
 
 #endif  // CHROME_BROWSER_METRICS_VARIATIONS_SERVICE_H_