Reverting 3174. Aka reapplying 3150, 3151 and 3159. Aka api accessor

src/x64/frames-x64.cc

Index: src/x64/frames-x64.cc
diff --git a/src/x64/frames-x64.cc b/src/x64/frames-x64.cc
index fe224ad998823a58aee088bd9c43056904056e09..6a0527cf6d666025b0b84ad3ecb168d560bd7e43 100644
--- a/src/x64/frames-x64.cc
+++ b/src/x64/frames-x64.cc
@@ -57,11 +57,7 @@ StackFrame::Type ExitFrame::GetStateForFramePointer(Address fp, State* state) {
   state->sp = sp;
   state->pc_address = reinterpret_cast<Address*>(sp - 1 * kPointerSize);
   // Determine frame type.
-  if (Memory::Address_at(fp + ExitFrameConstants::kDebugMarkOffset) != 0) {
-    return EXIT_DEBUG;
-  } else {
-    return EXIT;
-  }
+  return EXIT;
 }
 
 int JavaScriptFrame::GetProvidedParametersCount() const {
@@ -69,10 +65,10 @@ int JavaScriptFrame::GetProvidedParametersCount() const {
 }
 
 
-void ExitFrame::Iterate(ObjectVisitor* a) const {
-  // Exit frames on X64 do not contain any pointers. The arguments
-  // are traversed as part of the expression stack of the calling
-  // frame.
+void ExitFrame::Iterate(ObjectVisitor* v) const {
+  v->VisitPointer(&code_slot());
+  // The arguments are traversed as part of the expression stack of
+  // the calling frame.
 }
 
 byte* InternalFrame::GetCallerStackPointer() const {