[builtins] move String.prototype[@@iterator] to C++ builtin

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index f7e1c746dd49f79fe31d6ffbb11aab5f24785557..9966717704672650d0e9f631701fe3b9521a1d34 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -607,7 +607,7 @@ Handle<String> Factory::NewProperSubString(Handle<String> str,
 #if VERIFY_HEAP
   if (FLAG_verify_heap) str->StringVerify();
 #endif
-  DCHECK(begin > 0 || end < str->length());
+  DCHECK(begin > 0 || end <= str->length());

[caitp, 2016/09/15 19:02:39]

this seems to be necessary to use this for the last two code units in the
string, but I'm not positive.

[Benedikt Meurer, 2016/09/16 03:16:37]

No that'd definitely be a bug, you'd read out of bounds for the string.

 
   str = String::Flatten(str);
 
@@ -734,6 +734,15 @@ Handle<ExternalOneByteString> Factory::NewNativeSourceString(
   return external_string;
 }
 
+Handle<JSStringIterator> Factory::NewJSStringIterator(Handle<String> string) {
+  Handle<Map> map(isolate()->native_context()->string_iterator_map());
+  Handle<JSStringIterator> iterator =
+      Handle<JSStringIterator>::cast(NewJSObjectFromMap(map));
+  iterator->set_string(*String::Flatten(string));
+  iterator->set_index(Smi::FromInt(0));
+
+  return iterator;
+}
 
 Handle<Symbol> Factory::NewSymbol() {
   CALL_HEAP_FUNCTION(
@@ -1732,6 +1741,15 @@ Handle<JSDataView> Factory::NewJSDataView() {
       JSDataView);
 }
 
+Handle<JSIteratorResult> Factory::NewJSIteratorResult(Handle<Object> value,
+                                                      bool done) {
+  Handle<Map> map(isolate()->native_context()->iterator_result_map());
+  Handle<JSIteratorResult> js_iter_result =
+      Handle<JSIteratorResult>::cast(NewJSObjectFromMap(map));
+  js_iter_result->set_value(*value);
+  js_iter_result->set_done(*ToBoolean(done));
+  return js_iter_result;
+}
 
 Handle<JSMap> Factory::NewJSMap() {
   Handle<Map> map(isolate()->native_context()->js_map_map());