Use toString tag to format receiver in stack traces

src/runtime/runtime-object.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
@@ skipping 740 matching lines @@
 
 // Return property without being observable by accessors or interceptors.
 RUNTIME_FUNCTION(Runtime_GetDataProperty) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
   CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
   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);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(HeapObject, obj, 0);
   return isolate->heap()->ToBoolean(
       IsFastPackedElementsKind(obj->map()->elements_kind()));
 }
 
 
@@ skipping 225 matching lines @@
       isolate, o, key, &success, LookupIterator::OWN);
   if (!success) return isolate->heap()->exception();
   MAYBE_RETURN(
       JSReceiver::CreateDataProperty(&it, value, Object::THROW_ON_ERROR),
       isolate->heap()->exception());
   return *value;
 }
 
 }  // namespace internal
 }  // namespace v8