Check for valid PC when stepping in the ARM sim debugger.

BUG=v8:2134
TEST=

Review URL: https://chromiumcodereview.appspot.com/10546169

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11821 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/simulator-arm.cc

-// Copyright 2011 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -276,7 +276,7 @@ void ArmDebugger::Debug() {
   // make them invisible to all commands.
   UndoBreakpoints();
 
-  while (!done) {
+  while (!done && !sim_->has_bad_pc()) {
     if (last_pc != sim_->get_pc()) {
       disasm::NameConverter converter;
       disasm::Disassembler dasm(converter);