Reverting 3159, 3151 and 3150

src/frames.h

Index: src/frames.h
===================================================================
--- src/frames.h	(revision 3173)
+++ src/frames.h	(working copy)
@@ -93,6 +93,7 @@
   V(ENTRY,             EntryFrame)            \
   V(ENTRY_CONSTRUCT,   EntryConstructFrame)   \
   V(EXIT,              ExitFrame)             \
+  V(EXIT_DEBUG,        ExitDebugFrame)        \
   V(JAVA_SCRIPT,       JavaScriptFrame)       \
   V(INTERNAL,          InternalFrame)         \
   V(CONSTRUCT,         ConstructFrame)        \
@@ -118,6 +119,7 @@
   bool is_entry() const { return type() == ENTRY; }
   bool is_entry_construct() const { return type() == ENTRY_CONSTRUCT; }
   bool is_exit() const { return type() == EXIT; }
+  bool is_exit_debug() const { return type() == EXIT_DEBUG; }
   bool is_java_script() const { return type() == JAVA_SCRIPT; }
   bool is_arguments_adaptor() const { return type() == ARGUMENTS_ADAPTOR; }
   bool is_internal() const { return type() == INTERNAL; }
@@ -258,13 +260,10 @@
 // Exit frames are used to exit JavaScript execution and go to C.
 class ExitFrame: public StackFrame {
  public:
-  enum Mode { MODE_NORMAL, MODE_DEBUG };
   virtual Type type() const { return EXIT; }
 
   virtual Code* code() const;
 
-  Object*& code_slot() const;
-
   // Garbage collection support.
   virtual void Iterate(ObjectVisitor* v) const;
 
@@ -290,6 +289,26 @@
 };
 
 
+class ExitDebugFrame: public ExitFrame {
+ public:
+  virtual Type type() const { return EXIT_DEBUG; }
+
+  virtual Code* code() const;
+
+  static ExitDebugFrame* cast(StackFrame* frame) {
+    ASSERT(frame->is_exit_debug());
+    return static_cast<ExitDebugFrame*>(frame);
+  }
+
+ protected:
+  explicit ExitDebugFrame(StackFrameIterator* iterator)
+      : ExitFrame(iterator) { }
+
+ private:
+  friend class StackFrameIterator;
+};
+
+
 class StandardFrame: public StackFrame {
  public:
   // Testers.