Add faster, but unsafe version of LoadInternalField.

src/api-experimental.cc

Index: src/api-experimental.cc
diff --git a/src/api-experimental.cc b/src/api-experimental.cc
index 39284342702273c23631768d8880d28f00bff3bf..9b36ca40bf8e8c937698d880c2195d37563696a2 100644
--- a/src/api-experimental.cc
+++ b/src/api-experimental.cc
@@ -76,6 +76,10 @@ FastAccessorBuilder::ValueId FastAccessorBuilder::LoadInternalField(
   return FromApi(this)->LoadInternalField(value, field_no);
 }
 
+FastAccessorBuilder::ValueId FastAccessorBuilder::LoadInternalFieldUnchecked(
+    ValueId value, int field_no) {
+  return FromApi(this)->LoadInternalFieldUnchecked(value, field_no);
+}
 
 FastAccessorBuilder::ValueId FastAccessorBuilder::LoadValue(ValueId value_id,
                                                             int offset) {