Fix uninitialized field in Debug::ThreadInit().

Originally reported by Maxim.Mossienko on the isolates branch.

Review URL: http://codereview.chromium.org/3164020

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5288 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/debug.cc

@@ -551,6 +551,7 @@ void Debug::ThreadInit() {
   thread_local_.after_break_target_ = 0;
   thread_local_.debugger_entry_ = NULL;
   thread_local_.pending_interrupts_ = 0;
+  thread_local_.restarter_frame_function_pointer_ = NULL;
 }