Reset some UMA stability stats on a version change.

components/metrics/metrics_provider.h

Index: components/metrics/metrics_provider.h
diff --git a/components/metrics/metrics_provider.h b/components/metrics/metrics_provider.h
index abfbc6f63f55d0be929d11d73d5d48b8350db1f2..e9c27e3ae8181f6ded727171223b58f86793a473 100644
--- a/components/metrics/metrics_provider.h
+++ b/components/metrics/metrics_provider.h
@@ -43,6 +43,10 @@ class MetricsProvider {
   virtual void ProvideStabilityMetrics(
       SystemProfileProto* system_profile_proto);
 
+  // Called to indicate that saved stability prefs should be cleared, for e.g.

[Ilya Sherman, 2014/09/18 18:30:19]

nit: "for e.g. if" -> "e.g. because" -- at least, that reads more naturally to
me

[Alexei Svitkine (slow), 2014/09/18 20:21:14]

Done.

+  // if they are from an old version and should not be kept.
+  virtual void ClearSavedStabilityMetrics();
+
   // Provides general metrics that are neither system profile nor stability
   // metrics.
   virtual void ProvideGeneralMetrics(