Fix Debug::Break crash.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 3909da6a7c1f0fb833125dc7d10447f623b9ede6..93479d89a7daa1e009983eda722e73104a4decd0 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -4893,7 +4893,9 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_StoreArrayLiteralElement) {
 // to a built-in function such as Array.forEach.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugCallbackSupportsStepping) {
 #ifdef ENABLE_DEBUGGER_SUPPORT
-  if (!isolate->IsDebuggerActive()) return isolate->heap()->false_value();
+  if (!isolate->IsDebuggerActive() || !isolate->debug()->StepInActive()) {
+    return isolate->heap()->false_value();
+  }
   CONVERT_ARG_CHECKED(Object, callback, 0);
   // We do not step into the callback if it's a builtin or not even a function.
   if (!callback->IsJSFunction() || JSFunction::cast(callback)->IsBuiltin()) {