Avoid some crashes when running without snapshots.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index adbe70223254978c4ca73ccc9771692fe4b20b8f..3f1d4f2b182e2fb5925eb3c9954acd0a6b9da654 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -1913,7 +1913,7 @@ void Debug::CreateScriptCache() {
   HeapIterator iterator;
   AssertNoAllocation no_allocation;
 
-  for (HeapObject* obj = iterator.Next(); obj != NULL; obj = iterator.Next()) {
+  for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
     if (obj->IsScript() && Script::cast(obj)->HasValidSource()) {
       script_cache_->Add(Handle<Script>(Script::cast(obj)));
       count++;