Introduce a special kind of frames for construct frames, e.g....

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 483)
+++ src/runtime.cc	(working copy)
@@ -2917,7 +2917,7 @@
     if (Debug::StepInActive()) {
       StackFrameIterator it;
       it.Advance();
-      ASSERT(InternalFrame::cast(it.frame())->is_construct_trampoline());
+      ASSERT(it.frame()->is_construct());
       it.Advance();
       if (it.frame()->fp() == Debug::step_in_fp()) {
         HandleScope scope;