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

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 5cd83324c6f9ac4f43f6eb92e6dff916ada77ecd..d7302dea3da0eb9c0c5c9ecb9938ffc53df17e62 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -393,8 +393,19 @@ Code* EntryConstructFrame::code() const {
 }
 
 
+Object*& ExitFrame::code_slot() const {
+  const int offset = ExitFrameConstants::kCodeOffset;
+  return Memory::Object_at(fp() + offset);
+}
+
+
 Code* ExitFrame::code() const {
-  return Heap::c_entry_code();
+  Object* code = code_slot();
+  if (code->IsSmi()) {
+    return Heap::c_entry_debug_break_code();
+  } else {
+    return Code::cast(code);
+  }
 }
 
 
@@ -412,11 +423,6 @@ Address ExitFrame::GetCallerStackPointer() const {
 }
 
 
-Code* ExitDebugFrame::code() const {
-  return Heap::c_entry_debug_break_code();
-}
-
-
 Address StandardFrame::GetExpressionAddress(int n) const {
   const int offset = StandardFrameConstants::kExpressionsOffset;
   return fp() + offset - n * kPointerSize;