[debugger] simplify debug stepping.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 33deae4e980df030d5f241a3811e1bd716e663d3..3beef6bcf94a129724946d4361e12d9bb4722cfa 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1770,10 +1770,9 @@ ExternalReference ExternalReference::mod_two_doubles_operation(
                                     BUILTIN_FP_FP_CALL));
 }
 
-
-ExternalReference ExternalReference::debug_step_in_enabled_address(
+ExternalReference ExternalReference::debug_last_step_action_address(
     Isolate* isolate) {
-  return ExternalReference(isolate->debug()->step_in_enabled_address());
+  return ExternalReference(isolate->debug()->last_step_action_address());
 }
 
 ExternalReference ExternalReference::debug_suspended_generator_address(