Starting a refactor to allow adding metrics on upload.

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 9daaaafce245636ebc9107eee945d49940a06354..bb8ae1637411cc40c990c68f2a163054572c9f92 100644
--- a/components/metrics/metrics_provider.h
+++ b/components/metrics/metrics_provider.h
@@ -29,6 +29,9 @@ class MetricsProvider {
   // Called when metrics recording has been disabled.
   virtual void OnRecordingDisabled();
 
+  // Called by MetricsService when it is collecting final metrics.
+  virtual void OnCollectFinalMetrics();
+
   // Provides additional metrics into the system profile.
   virtual void ProvideSystemProfileMetrics(
       SystemProfileProto* system_profile_proto);