Improve array to string conversion.

src/json-stringifier.h

Index: src/json-stringifier.h
diff --git a/src/json-stringifier.h b/src/json-stringifier.h
index 80ef39507812207ac5dbaa690b51855bfd522793..2399395396aa28c601cd5a4a88c07a85e12cbfc5 100644
--- a/src/json-stringifier.h
+++ b/src/json-stringifier.h
@@ -603,26 +603,7 @@ void BasicJsonStringifier::ShrinkCurrentPart() {
     return;
   }
 
-  int string_size, allocated_string_size;
-  if (is_ascii_) {
-    allocated_string_size = SeqOneByteString::SizeFor(part_length_);
-    string_size = SeqOneByteString::SizeFor(current_index_);
-  } else {
-    allocated_string_size = SeqTwoByteString::SizeFor(part_length_);
-    string_size = SeqTwoByteString::SizeFor(current_index_);
-  }
-
-  int delta = allocated_string_size - string_size;
-  current_part_->set_length(current_index_);
-
-  // String sizes are pointer size aligned, so that we can use filler objects
-  // that are a multiple of pointer size.
-  Address end_of_string = current_part_->address() + string_size;
-  isolate_->heap()->CreateFillerObjectAt(end_of_string, delta);
-  if (Marking::IsBlack(Marking::MarkBitFrom(*current_part_))) {
-    MemoryChunk::IncrementLiveBytesFromMutator(
-        current_part_->address(), -delta);
-  }
+  SeqString::cast(*current_part_)->Truncate(current_index_);

[Toon Verwaest, 2012/12/05 14:29:12]

Runtime_Truncate returns the resulting string; and does not support length == 0.
This function on the other hand does support length == 0; and relies on the
internal truncate that does not handle == 0. Can we just unify it all and
support length == 0 directly in the Truncate called here, and make it return the
new string? That way we can just support truncation to length == 0 in
Runtime_Truncate as well and don't need external checks. Then we can also remove
this utility function and just call truncate directly where you'd call
ShrinkCurrentPart.

 }