Allow setting accessor infos over read-only but configurable properties.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index d60fb7c1aaa356611a6d8d8f4115a2cfeb16dbef..0aa2da678656aac9189f2fb5863de0a4ba718a17 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -6346,7 +6346,7 @@ MaybeHandle<Object> JSObject::SetAccessor(Handle<JSObject> object,
 
   // ES5 forbids turning a property into an accessor if it's not
   // configurable. See 8.6.1 (Table 5).
-  if (it.IsFound() && (it.IsReadOnly() || !it.IsConfigurable())) {
+  if (it.IsFound() && !it.IsConfigurable()) {
     return it.factory()->undefined_value();
   }