diff --git a/buffet/states/state_change_queue_interface.h b/buffet/states/state_change_queue_interface.h
index 5810bff..84704dd 100644
--- a/buffet/states/state_change_queue_interface.h
+++ b/buffet/states/state_change_queue_interface.h
@@ -14,12 +14,14 @@
 
 // A simple notification record event to track device state changes.
 // The |timestamp| records the time of the state change.
-// |property_set| contains a property set with the new property values.
-// The property set contains only the properties updated at the time the event
-// was recorded.
+// |changed_properties| contains a property set with the new property values
+// which were updated at the time the event was recorded.
 struct StateChange {
+  StateChange(base::Time time,
+              chromeos::VariantDictionary properties)
+    : timestamp(time), changed_properties(std::move(properties)) {}
   base::Time timestamp;
-  chromeos::VariantDictionary property_set;
+  chromeos::VariantDictionary changed_properties;
 };
 
 // An abstract interface to StateChangeQueue to record and retrieve state
@@ -30,7 +32,9 @@
   virtual bool IsEmpty() const = 0;
 
   // Called by StateManager when device state properties are updated.
-  virtual bool NotifyPropertiesUpdated(const StateChange& change) = 0;
+  virtual bool NotifyPropertiesUpdated(
+      base::Time timestamp,
+      chromeos::VariantDictionary changed_properties) = 0;
 
   // Returns the recorded state changes since last time this method was called.
   virtual std::vector<StateChange> GetAndClearRecordedStateChanges() = 0;