Ensure double arrays are filled with holes when extended from variations of empty arrays.

src/elements.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 357 matching lines @@
                                           int packed_size,
                                           int raw_copy_size) {
   int copy_size = raw_copy_size;
   uint32_t to_end;
   if (raw_copy_size < 0) {
     ASSERT(raw_copy_size == ElementsAccessor::kCopyToEnd ||
            raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole);
     copy_size = from->length() - from_start;
     if (raw_copy_size == ElementsAccessor::kCopyToEndAndInitializeToHole) {
       to_end = to->length();
+      for (uint32_t i = to_start + copy_size; i < to_end; ++i) {
+        to->set_the_hole(i);
+      }
     } else {
       to_end = to_start + static_cast<uint32_t>(copy_size);
     }
   } else {
     to_end = to_start + static_cast<uint32_t>(copy_size);
   }
   ASSERT(static_cast<int>(to_end) <= to->length());
   ASSERT(packed_size >= 0 && packed_size <= copy_size);
   ASSERT((copy_size + static_cast<int>(to_start)) <= to->length() &&
          (copy_size + static_cast<int>(from_start)) <= from->length());
   if (copy_size == 0) return;
   for (uint32_t from_end = from_start + static_cast<uint32_t>(packed_size);
        from_start < from_end; from_start++, to_start++) {
     Object* smi = from->get(from_start);
     ASSERT(!smi->IsTheHole());
     to->set(to_start, Smi::cast(smi)->value());
   }
-
-  while (to_start < to_end) {
-    to->set_the_hole(to_start++);
-  }
 }
 
 
 static void CopyObjectToDoubleElements(FixedArray* from,
                                        uint32_t from_start,
                                        FixedDoubleArray* to,
                                        uint32_t to_start,
                                        int raw_copy_size) {
   int copy_size = raw_copy_size;
   if (raw_copy_size < 0) {
@@ skipping 1447 matching lines @@
   if (!maybe_obj->To(&new_backing_store)) return maybe_obj;
   new_backing_store->set(0, length);
   { MaybeObject* result = array->SetContent(new_backing_store);
     if (result->IsFailure()) return result;
   }
   return array;
 }
 
 
 } }  // namespace v8::internal