[UMA, Cleanup] Deprecate the UMA.GeneratedLowEntropySource histogram.

components/metrics/metrics_state_manager.h

Index: components/metrics/metrics_state_manager.h
diff --git a/components/metrics/metrics_state_manager.h b/components/metrics/metrics_state_manager.h
index 041831c52fbbf0587b51427d210ef8e962909980..fd80c235208b1c446d27e8753c6d33aa7d2a4e1d 100644
--- a/components/metrics/metrics_state_manager.h
+++ b/components/metrics/metrics_state_manager.h
@@ -117,6 +117,10 @@ class MetricsStateManager {
   // generate the entropy source value if it has not been called before.
   int GetLowEntropySource();
 
+  // Generates the low entropy source value for this client if it is not
+  // already set.
+  void UpdateLowEntropySource();
+
   // Updates |entropy_source_returned_| with |type| iff the current value is
   // ENTROPY_SOURCE_NONE and logs the new value in a histogram.
   void UpdateEntropySourceReturnedValue(EntropySourceType type);