Add gdb helper functions for creating a handle and using ToCString with RawObjects.

runtime/lib/object.cc

Index: runtime/lib/object.cc
diff --git a/runtime/lib/object.cc b/runtime/lib/object.cc
index b7dcea3a2088351939f96dbb7ef5d1c8b07932bf..70fe890f8dce44f45cd31fdfba175ea279c165e1 100644
--- a/runtime/lib/object.cc
+++ b/runtime/lib/object.cc
@@ -17,15 +17,11 @@ namespace dart {
 
 DECLARE_FLAG(bool, trace_type_checks);
 
-// Helper function in stacktrace.cc.
-void _printCurrentStackTrace();
-
 DEFINE_NATIVE_ENTRY(DartAsync_fatal, 1) {
   // The dart:async library code entered an unrecoverable state.
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
   const char* msg = instance.ToCString();
   OS::PrintErr("Fatal error in dart:async: %s\n", msg);
-  _printCurrentStackTrace();
   FATAL(msg);
   return Object::null();
 }