new classes: no longer experimental.

src/arm/builtins-arm.cc

Index: src/arm/builtins-arm.cc
diff --git a/src/arm/builtins-arm.cc b/src/arm/builtins-arm.cc
index 1203ec42b3d3523ce46f66f28a7aed4be271bf79..ba92ff8e34f326c483d710f4d6f16482e343e746 100644
--- a/src/arm/builtins-arm.cc
+++ b/src/arm/builtins-arm.cc
@@ -788,10 +788,29 @@ void Builtins::Generate_JSConstructStubForDerived(MacroAssembler* masm) {
     __ sub(r4, r4, Operand(2), SetCC);
     __ b(ge, &loop);
 
+    __ add(r0, r0, Operand(1));
+
+    // Handle step in.
+    Label skip_step_in;
+    ExternalReference debug_step_in_fp =
+        ExternalReference::debug_step_in_fp_address(masm->isolate());
+    __ mov(r2, Operand(debug_step_in_fp));
+    __ ldr(r2, MemOperand(r2));
+    __ tst(r2, r2);
+    __ b(eq, &skip_step_in);
+
+    __ Push(r0);
+    __ Push(r1);
+    __ Push(r1);
+    __ CallRuntime(Runtime::kHandleStepInForDerivedConstructors, 1);
+    __ Pop(r1);
+    __ Pop(r0);
+
+    __ bind(&skip_step_in);
+
     // Call the function.
     // r0: number of arguments
     // r1: constructor function
-    __ add(r0, r0, Operand(1));
     ParameterCount actual(r0);
     __ InvokeFunction(r1, actual, CALL_FUNCTION, NullCallWrapper());