Do not visit smis in the root list during GC.

src/heap-inl.h

 // 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:
 //
 //     * 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 802 matching lines @@
   for (Object** current = start; current < end; current++) {
     if ((*current)->IsHeapObject()) {
       HeapObject* object = HeapObject::cast(*current);
       CHECK(object->GetIsolate()->heap()->Contains(object));
       CHECK(object->map()->IsMap());
     }
   }
 }
 
 
+void VerifySmisVisitor::VisitPointers(Object** start, Object** end) {
+  for (Object** current = start; current < end; current++) {
+     CHECK((*current)->IsSmi());
+  }
+}
+
+
 double GCTracer::SizeOfHeapObjects() {
   return (static_cast<double>(heap_->SizeOfObjects())) / MB;
 }
 
 
 DisallowAllocationFailure::DisallowAllocationFailure() {
 #ifdef DEBUG
   Isolate* isolate = Isolate::Current();
   old_state_ = isolate->heap()->disallow_allocation_failure_;
   isolate->heap()->disallow_allocation_failure_ = true;
 #endif
 }
 
 
 DisallowAllocationFailure::~DisallowAllocationFailure() {
 #ifdef DEBUG
   Isolate* isolate = Isolate::Current();
   isolate->heap()->disallow_allocation_failure_ = old_state_;
 #endif
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_