BootControl: is slot marked successful

Test: update_engine_unittests
Bug: 147696014

Change-Id: I316efda7a0936e2dee0f766efb5c18ff30790274
Merged-In: I316efda7a0936e2dee0f766efb5c18ff30790274
diff --git a/boot_control_chromeos.h b/boot_control_chromeos.h
index 10454be..0209052 100644
--- a/boot_control_chromeos.h
+++ b/boot_control_chromeos.h
@@ -52,6 +52,7 @@
   bool MarkSlotUnbootable(BootControlInterface::Slot slot) override;
   bool SetActiveBootSlot(BootControlInterface::Slot slot) override;
   bool MarkBootSuccessfulAsync(base::Callback<void(bool)> callback) override;
+  bool IsSlotMarkedSuccessful(BootControlInterface::Slot slot) const override;
   DynamicPartitionControlInterface* GetDynamicPartitionControl() override;
 
  private: