BootControl: is slot marked successful

Test: update_engine_unittests
Bug: 147696014

Change-Id: I316efda7a0936e2dee0f766efb5c18ff30790274
diff --git a/common/boot_control_stub.cc b/common/boot_control_stub.cc
index d198e9d..2eb9211 100644
--- a/common/boot_control_stub.cc
+++ b/common/boot_control_stub.cc
@@ -63,6 +63,11 @@
   return false;
 }
 
+bool BootControlStub::IsSlotMarkedSuccessful(Slot slot) const {
+  LOG(ERROR) << __FUNCTION__ << " should never be called.";
+  return false;
+}
+
 DynamicPartitionControlInterface*
 BootControlStub::GetDynamicPartitionControl() {
   return dynamic_partition_control_.get();