Cleanup the way the debugger stores live registers when entering at a break...

src/debug.h

Index: src/debug.h
===================================================================
--- src/debug.h	(revision 5352)
+++ src/debug.h	(working copy)
@@ -332,8 +332,7 @@
     k_after_break_target_address,
     k_debug_break_return_address,
     k_debug_break_slot_address,
-    k_restarter_frame_function_pointer,
-    k_register_address
+    k_restarter_frame_function_pointer
   };
 
   // Support for setting the address to jump to when returning from break point.
@@ -953,10 +952,7 @@
 // code.
 class Debug_Address {
  public:
-  Debug_Address(Debug::AddressId id, int reg = 0)
-    : id_(id), reg_(reg) {
-    ASSERT(reg == 0 || id == Debug::k_register_address);
-  }
+  Debug_Address(Debug::AddressId id) : id_(id) { }
 
   static Debug_Address AfterBreakTarget() {
     return Debug_Address(Debug::k_after_break_target_address);
@@ -970,10 +966,6 @@
     return Debug_Address(Debug::k_restarter_frame_function_pointer);
   }
 
-  static Debug_Address Register(int reg) {
-    return Debug_Address(Debug::k_register_address, reg);
-  }
-
   Address address() const {
     switch (id_) {
       case Debug::k_after_break_target_address:
@@ -985,8 +977,6 @@
       case Debug::k_restarter_frame_function_pointer:
         return reinterpret_cast<Address>(
             Debug::restarter_frame_function_pointer_address());
-      case Debug::k_register_address:
-        return reinterpret_cast<Address>(Debug::register_address(reg_));
       default:
         UNREACHABLE();
         return NULL;
@@ -994,7 +984,6 @@
   }
  private:
   Debug::AddressId id_;
-  int reg_;
 };
 
 // The optional thread that Debug Agent may use to temporary call V8 to process