Use toString tag to format receiver in stack traces

src/runtime/runtime-object.cc

Index: src/runtime/runtime-object.cc
diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc
index 761008aa63d69504a66a0db284b6561135fbae8f..bfc35907cfd064ef41b5acaa47144d77e08dd759 100644
--- a/src/runtime/runtime-object.cc
+++ b/src/runtime/runtime-object.cc
@@ -758,6 +758,16 @@ RUNTIME_FUNCTION(Runtime_GetDataProperty) {
   return *JSReceiver::GetDataProperty(object, name);
 }
 
+RUNTIME_FUNCTION(Runtime_GetConstructorName) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+
+  Handle<JSReceiver> recv;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, recv,

[Yang, 2016/07/04 10:55:38]

Can this actually throw? If it does, should we catch that and instead return
some default string?

[jgruber, 2016/07/04 12:40:19]

Apparently, Object::ToObject() throws if null or undefined are passed. We ensure
this is not the case in messages.js:GetTypeName(). Added a CHECK here and
removed the ASSIGN_RETURN_FAILURE_ON_EXCEPTION use.

+                                     Object::ToObject(isolate, object));
+  return *JSReceiver::GetConstructorName(recv);
+}
 
 RUNTIME_FUNCTION(Runtime_HasFastPackedElements) {
   SealHandleScope shs(isolate);