A change in the way we place TransitionElementKinds in the tree.

src/elements-kind.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 193 matching lines @@
 bool IsMoreGeneralElementsKindTransition(ElementsKind from_kind,
                                          ElementsKind to_kind);
 
 
 inline bool IsTransitionableFastElementsKind(ElementsKind from_kind) {
   return IsFastElementsKind(from_kind) &&
       from_kind != TERMINAL_FAST_ELEMENTS_KIND;
 }
 
 
+// Return the closest fast elements kind that can be transitioned to from both
+// kind1 and kind2. For example, kind1 is a SMI, kind2 is a DOUBLE, then
+// return DOUBLE. If kind1 is a HOLEY_SMI and kind2 is a DOUBLE, return
+// HOLEY_DOUBLE.
+ElementsKind GetUnifiedFastElementsKind(ElementsKind kind1, ElementsKind kind2);
+
 ElementsKind GetNextMoreGeneralFastElementsKind(ElementsKind elements_kind,
                                                 bool allow_only_packed);
 
 
 inline bool CanTransitionToMoreGeneralFastElementsKind(
     ElementsKind elements_kind,
     bool allow_only_packed) {
   return IsFastElementsKind(elements_kind) &&
       (elements_kind != TERMINAL_FAST_ELEMENTS_KIND &&
        (!allow_only_packed || elements_kind != FAST_ELEMENTS));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ELEMENTS_KIND_H_