BootControl: is slot marked successful

Test: update_engine_unittests
Bug: 147696014

Change-Id: I316efda7a0936e2dee0f766efb5c18ff30790274
diff --git a/boot_control_chromeos.cc b/boot_control_chromeos.cc
index e972d41..0f47169 100644
--- a/boot_control_chromeos.cc
+++ b/boot_control_chromeos.cc
@@ -329,6 +329,11 @@
   return -1;
 }
 
+bool BootControlChromeOS::IsSlotMarkedSuccessful(Slot slot) const {
+  LOG(ERROR) << __func__ << " not supported.";
+  return false;
+}
+
 DynamicPartitionControlInterface*
 BootControlChromeOS::GetDynamicPartitionControl() {
   return dynamic_partition_control_.get();