Do not visit smis in the root list during GC.

src/objects.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 10618 matching lines @@
 
 
 #undef DECL_BOOLEAN_ACCESSORS
 #undef DECL_ACCESSORS
 #undef DECLARE_VERIFIER
 
 #define VISITOR_SYNCHRONIZATION_TAGS_LIST(V)                            \
   V(kStringTable, "string_table", "(Internalized strings)")             \
   V(kExternalStringsTable, "external_strings_table", "(External strings)") \
   V(kStrongRootList, "strong_root_list", "(Strong roots)")              \
+  V(kSmiRootList, "smi_root_list", "(Smi roots)")                       \
   V(kInternalizedString, "internalized_string", "(Internal string)")    \
   V(kBootstrapper, "bootstrapper", "(Bootstrapper)")                    \
   V(kTop, "top", "(Isolate)")                                           \
   V(kRelocatable, "relocatable", "(Relocatable)")                       \
   V(kDebug, "debug", "(Debugger)")                                      \
   V(kCompilationCache, "compilationcache", "(Compilation cache)")       \
   V(kHandleScope, "handlescope", "(Handle scope)")                      \
   V(kBuiltins, "builtins", "(Builtins)")                                \
   V(kGlobalHandles, "globalhandles", "(Global handles)")                \
   V(kEternalHandles, "eternalhandles", "(Eternal handles)")             \
@@ skipping 104 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_