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

chrome/browser/metrics/variations_service.cc

 // 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.
 
 #include "chrome/browser/metrics/variations_service.h"
 
 #include <set>
 
 #include "base/base64.h"
 #include "base/build_time.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/version.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/metrics/proto/trials_seed.pb.h"
 #include "chrome/browser/prefs/pref_service.h"
+#include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/metrics/experiments_helper.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_service.h"
 #include "content/public/common/url_fetcher.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/load_flags.h"
 #include "net/base/network_change_notifier.h"
 #include "net/http/http_response_headers.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_status.h"
 
 namespace chrome_variations {
 
@@ skipping 59 matching lines @@
     server_url = kDefaultVariationsServerURL;
   GURL url_as_gurl = GURL(server_url);
   DCHECK(url_as_gurl.is_valid());
   return url_as_gurl;
 }
 
 }  // namespace
 
 VariationsService::VariationsService()
     : variations_server_url_(GetVariationsServerURL()) {
+  registrar_.Add(this, chrome::NOTIFICATION_UPGRADE_RECOMMENDED,
+                 content::NotificationService::AllSources());
 }
 
 VariationsService::~VariationsService() {}
 
 bool VariationsService::CreateTrialsFromSeed(PrefService* local_prefs) {
   TrialsSeed seed;
   if (!LoadTrialsSeedFromPref(local_prefs, &seed))
     return false;
 
   const int64 date_value = local_prefs->GetInt64(prefs::kVariationsSeedDate);
@@ skipping 74 matching lines @@
   StoreSeedData(seed_data, response_date, g_browser_process->local_state());
 }
 
 // static
 void VariationsService::RegisterPrefs(PrefService* prefs) {
   prefs->RegisterStringPref(prefs::kVariationsSeed, std::string());
   prefs->RegisterInt64Pref(prefs::kVariationsSeedDate,
                            base::Time().ToInternalValue());
 }
 
+void VariationsService::Observe(int type,

[Alexei Svitkine (slow), 2012/07/23 14:42:43]

Please define this in the same order as functions are declared in the header
file.

[SteveT, 2012/07/23 15:24:31]

Uh... this is already in the correct place?

[Alexei Svitkine (slow), 2012/07/23 15:32:13]

Oops, you're right - I must have misread the order. My bad.

+                                const content::NotificationSource& source,
+                                const content::NotificationDetails& details) {

[Alexei Svitkine (slow), 2012/07/23 14:42:43]

Is this guaranteed to be called on the UI thread?

[SteveT, 2012/07/23 15:24:31]

I believe it is, though I'll have to check to make sure. I've added a DCHECK to
assert this.

+  DCHECK(type == chrome::NOTIFICATION_UPGRADE_RECOMMENDED);
+  // An upgrade is ready, so attempt to fetch the Variations seed in case there
+  // were updates.
+  FetchVariationsSeed();
+  timer_.Reset();

[Alexei Svitkine (slow), 2012/07/23 14:42:43]

Nit: Add a comment explaining timer resetting.

[SteveT, 2012/07/23 15:24:31]

Done.

+}
+
 bool VariationsService::StoreSeedData(const std::string& seed_data,
                                       const base::Time& seed_date,
                                       PrefService* local_prefs) {
   // Only store the seed data if it parses correctly.
   TrialsSeed seed;
   if (!seed.ParseFromString(seed_data)) {
     VLOG(1) << "Variations Seed data from server is not in valid proto format, "
             << "rejecting the seed.";
     return false;
   }
@@ skipping 244 matching lines @@
                                                           variation_id);
     }
   }
 
   trial->SetForced();
   if (IsStudyExpired(study, reference_date))
     trial->Disable();
 }
 
 }  // namespace chrome_variations