Avoid some crashes when running without snapshots.

src/debug.cc

 // Copyright 2011 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1895 matching lines @@
   heap->CollectAllGarbage(Heap::kMakeHeapIterableMask);
 
   ASSERT(script_cache_ == NULL);
   script_cache_ = new ScriptCache();
 
   // Scan heap for Script objects.
   int count = 0;
   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++;
     }
   }
 }
 
 
 void Debug::DestroyScriptCache() {
   // Get rid of the script cache if it was created.
@@ skipping 1203 matching lines @@
     {
       Locker locker;
       Isolate::Current()->debugger()->CallMessageDispatchHandler();
     }
   }
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal