Expose a method in VariationsService to trigger a seed fetch.

chrome/browser/metrics/variations/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_VARIATIONS_SERVICE_H_
 #define CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 35 matching lines @@
   // Calls FetchVariationsSeed once and repeats this periodically. See
   // implementation for details on the period. Must be called after
   // |CreateTrialsFromSeed|.
   void StartRepeatedVariationsSeedFetch();
 
   // Returns the variations server URL, which can vary if a command-line flag is
   // set and/or the variations restrict pref is set in |local_prefs|. Declared
   // static for test purposes.
   static GURL GetVariationsServerURL(PrefService* local_prefs);
 
+  // Potentially triggers a FetchVariationsSeed call. This may depend on how
+  // long it has been since the previous fetch occurred.
+  void ScheduleFetch();

[Alexei Svitkine (slow), 2014/02/12 16:22:47]

I prefer if this is done similarly to MetricsService, i.e. so that this listens
to OnAppEnterBackground()/OnAppEnterForeground().

That way, the logic of what to do on those events would be in VariationsService,
rather than external to it.

In the ideal world, it would be best if there was a standard API at the Chromium
C++ level to register for these events, rather needing custom plumbing for each
sort of thing that needs it.

+
 #if defined(OS_WIN)
   // Starts syncing Google Update Variation IDs with the registry.
   void StartGoogleUpdateRegistrySync();
 #endif
 
   // Exposed for testing.
   void SetCreateTrialsFromSeedCalledForTesting(bool called);
 
   // Exposed for testing.
   static std::string GetDefaultVariationsServerURLForTesting();
@@ skipping 77 matching lines @@
   // Helper that handles synchronizing Variations with the Registry.
   VariationsRegistrySyncer registry_syncer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(VariationsService);
 };
 
 }  // namespace chrome_variations
 
 #endif  // CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_