Improve SeqString::Truncate for latest allocated strings.

src/json-stringifier.h

Index: src/json-stringifier.h
diff --git a/src/json-stringifier.h b/src/json-stringifier.h
index 418d4794595367f088e09cbb519d65209ff7bd96..355c4fcb1fe9ca170e8d9a1573312afe5b55bbb0 100644
--- a/src/json-stringifier.h
+++ b/src/json-stringifier.h
@@ -322,15 +322,8 @@ MaybeObject* BasicJsonStringifier::StringifyString_(Isolate* isolate,
                                           dest->GetChars() + 1,
                                           string->length());
   dest->Set(final_size++, '\"');
-  if (isolate->heap()->InNewSpace(*result)) {
-    // In new space, simply lower the allocation top to fit the actual size.
-    isolate->heap()->new_space()->ShrinkStringAtAllocationBoundary<StringType>(
-        *result, final_size);
-    return *result;
-  } else {
-    // Not in new space, need to fill the wasted space with filler objects.
-    return SeqString::cast(*result)->Truncate(final_size);
-  }
+  SeqString::cast(*result)->Truncate(final_size);
+  return *result;
 }
 
 
@@ -697,8 +690,11 @@ BasicJsonStringifier::Result BasicJsonStringifier::SerializeJSObject(
 
 void BasicJsonStringifier::ShrinkCurrentPart() {
   ASSERT(current_index_ < part_length_);
-  current_part_ = Handle<String>(
-      SeqString::cast(*current_part_)->Truncate(current_index_), isolate_);
+  if (current_index_ == 0) {

[Hannes Payer (out of office), 2013/03/21 12:48:30]

Again, Truncate() should do the right thing for you.

+    current_part_ = isolate_->factory()->empty_string();
+  } else {
+    SeqString::cast(*current_part_)->Truncate(current_index_);
+  }
 }