MetricsReporter gets DynamicPartitionControl.

Test: TH
Bug: 178732971
Change-Id: If434927b7abdecb8093db1462dae196cd744331a
diff --git a/common/boot_control_interface.h b/common/boot_control_interface.h
index 3b61add..321174e 100644
--- a/common/boot_control_interface.h
+++ b/common/boot_control_interface.h
@@ -103,7 +103,7 @@
   // Check if |slot| is marked boot successfully.
   virtual bool IsSlotMarkedSuccessful(Slot slot) const = 0;
 
-  // Return the dynamic partition control interface.
+  // Return the dynamic partition control interface. Never null.
   virtual DynamicPartitionControlInterface* GetDynamicPartitionControl() = 0;
 
   // Return a human-readable slot name used for logging.