Fix array concat for holey arrays and concat of double to object arrays.

src/objects.cc

 // 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 10471 matching lines @@
 }
 
 
 MaybeObject* JSObject::TransitionElementsKind(ElementsKind to_kind) {
   ElementsKind from_kind = map()->elements_kind();
 
   if (IsFastHoleyElementsKind(from_kind)) {
     to_kind = GetHoleyElementsKind(to_kind);
   }
 
+  if (from_kind == to_kind) return this;
+
   Isolate* isolate = GetIsolate();
   if (elements() == isolate->heap()->empty_fixed_array() ||
       (IsFastSmiOrObjectElementsKind(from_kind) &&
        IsFastSmiOrObjectElementsKind(to_kind)) ||
       (from_kind == FAST_DOUBLE_ELEMENTS &&
        to_kind == FAST_HOLEY_DOUBLE_ELEMENTS)) {
     ASSERT(from_kind != TERMINAL_FAST_ELEMENTS_KIND);
     // No change is needed to the elements() buffer, the transition
     // only requires a map change.
     MaybeObject* maybe_new_map = GetElementsTransitionMap(isolate, to_kind);
@@ skipping 3377 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal