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

chrome/browser/metrics/variations_service.cc

Index: chrome/browser/metrics/variations_service.cc
diff --git a/chrome/browser/metrics/variations_service.cc b/chrome/browser/metrics/variations_service.cc
index 5ee2ee13fa8ec28026d9dd672fb2121520cf63ea..1361198c8c15a3fb18a303cb9a74cf0782099b58 100644
--- a/chrome/browser/metrics/variations_service.cc
+++ b/chrome/browser/metrics/variations_service.cc
@@ -16,10 +16,12 @@
 #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"
@@ -99,6 +101,8 @@ GURL GetVariationsServerURL() {
 
 VariationsService::VariationsService()
     : variations_server_url_(GetVariationsServerURL()) {
+  registrar_.Add(this, chrome::NOTIFICATION_UPGRADE_RECOMMENDED,
+                 content::NotificationService::AllSources());
 }
 
 VariationsService::~VariationsService() {}
@@ -193,6 +197,16 @@ void VariationsService::RegisterPrefs(PrefService* prefs) {
                            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) {