Reverting 3159, 3151 and 3150

src/frames.cc

Index: src/frames.cc
===================================================================
--- src/frames.cc	(revision 3173)
+++ src/frames.cc	(working copy)
@@ -393,19 +393,8 @@
 }
 
 
-Object*& ExitFrame::code_slot() const {
-  const int offset = ExitFrameConstants::kCodeOffset;
-  return Memory::Object_at(fp() + offset);
-}
-
-
 Code* ExitFrame::code() const {
-  Object* code = code_slot();
-  if (code->IsSmi()) {
-    return Heap::c_entry_debug_break_code();
-  } else {
-    return Code::cast(code);
-  }
+  return Heap::c_entry_code();
 }
 
 
@@ -423,6 +412,11 @@
 }
 
 
+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;