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

chrome/browser/metrics/variations_service.h

Index: chrome/browser/metrics/variations_service.h
diff --git a/chrome/browser/metrics/variations_service.h b/chrome/browser/metrics/variations_service.h
index a431a6dd1498625bf167cd921b22b90428d064bb..ae465e6a6c42e8e3b9d01ac097257f9ea4c77bab 100644
--- a/chrome/browser/metrics/variations_service.h
+++ b/chrome/browser/metrics/variations_service.h
@@ -16,6 +16,8 @@
 #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"
 
@@ -29,7 +31,8 @@ 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();
@@ -43,16 +46,20 @@ class VariationsService : public net::URLFetcherDelegate {
   // 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);
 
+ protected:
+  // Starts the fetching process once, where |OnURLFetchComplete| is called with
+  // the response. This is protected so we can override this for testing
+  // purposes.
+  virtual void FetchVariationsSeed();
+
+  // Overridden from content::NotificationObserver:
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
  private:
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyChannel);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, CheckStudyLocale);
@@ -65,6 +72,9 @@ class VariationsService : public net::URLFetcherDelegate {
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, StoreSeed);
   FRIEND_TEST_ALL_PREFIXES(VariationsServiceTest, ValidateStudy);
 
+  // net::URLFetcherDelegate implementation:

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

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

[SteveT, 2012/07/24 14:42:58]

Done.

+  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
@@ -131,6 +141,9 @@ class VariationsService : public net::URLFetcherDelegate {
   // 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