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 cd60a26d318b328bd8c1ff9a804288be28bf3e7c..ee9799460e658454cc7972b5d94cadd1d8dc0d9a 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"
@@ -100,6 +102,8 @@ GURL GetVariationsServerURL() {
 VariationsService::VariationsService()
     : variations_server_url_(GetVariationsServerURL()),
       create_trials_from_seed_called_(false) {
+  registrar_.Add(this, chrome::NOTIFICATION_UPGRADE_RECOMMENDED,
+                 content::NotificationService::AllSources());

[Ilya Sherman, 2012/08/07 20:31:51]

NotificationService::AllSources() is generally discouraged.  Do you know what
the source for this notification is?

[SteveT, 2012/08/08 18:11:39]

This is an UpgradeDetector, which conveniently is a Singleton, so I'll call
GetInstance here.

Note that none of the other listeners of NOTIFICATION_UPGRADE_RECOMMENDED have a
specific source... Do you think it'd be wise to (in a separate patch) change
them all to listen to UpgradeDetector::GetInstance() as a source?

[Ilya Sherman, 2012/08/08 21:33:47]

Lovely :)
Yes, that would be great -- thanks for offering to clean that up! :)

 }
 
 VariationsService::~VariationsService() {}
@@ -147,6 +151,13 @@ void VariationsService::StartRepeatedVariationsSeedFetch() {
                this, &VariationsService::FetchVariationsSeed);
 }
 
+// static
+void VariationsService::RegisterPrefs(PrefService* prefs) {
+  prefs->RegisterStringPref(prefs::kVariationsSeed, std::string());
+  prefs->RegisterInt64Pref(prefs::kVariationsSeedDate,
+                           base::Time().ToInternalValue());
+}
+
 void VariationsService::FetchVariationsSeed() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
@@ -171,6 +182,22 @@ void VariationsService::FetchVariationsSeed() {
   pending_seed_request_->Start();
 }
 
+void VariationsService::Observe(int type,
+                                const content::NotificationSource& source,
+                                const content::NotificationDetails& details) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  DCHECK(type == chrome::NOTIFICATION_UPGRADE_RECOMMENDED);

[Ilya Sherman, 2012/08/07 20:31:51]

nit: DCHECK_EQ(chrome::NOTIFICATION_UPGRADE_RECOMMENDED, type);

[SteveT, 2012/08/08 18:11:39]

Done.

+
+  // An upgrade is ready, so attempt to fetch the Variations seed in case there

[Ilya Sherman, 2012/08/07 20:31:51]

Out of curiosity, when do we capitalize jargon like "variations", "seed", etc.? 
(Obviously not a big deal, I'm just curious.)

[SteveT, 2012/08/08 18:11:39]

Hm, good question. I think in this file we're sort of using it as the name for
the feature (as opposed to the internal code name), so that's why we capitalize
it. This is not consistent, though, so I've capitalized "variations" across this
file.

Do push back if you think we're breaking some important style guide/grammar rule
:)

[Ilya Sherman, 2012/08/08 21:33:47]

Nope, was just curious.  Thanks :)

+  // were updates.
+  FetchVariationsSeed();
+
+  // Since we explicitly call FetchVariationsSeed here, we can reset the timer
+  // so that we don't retry for another full period.
+  if (timer_.IsRunning())
+    timer_.Reset();
+}
+
 void VariationsService::OnURLFetchComplete(const net::URLFetcher* source) {
   DCHECK_EQ(pending_seed_request_.get(), source);
   // When we're done handling the request, the fetcher will be deleted.
@@ -198,13 +225,6 @@ void VariationsService::OnURLFetchComplete(const net::URLFetcher* source) {
   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());
-}
-
 bool VariationsService::StoreSeedData(const std::string& seed_data,
                                       const base::Time& seed_date,
                                       PrefService* local_prefs) {