[proxies] Improve error messages.

src/runtime/runtime-proxy.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/elements.h"
 #include "src/factory.h"
 #include "src/isolate-inl.h"
@@ skipping 116 matching lines @@
   // 8. Let newObj be ? Call(trap, handler, «target, argArray, newTarget »).
   Handle<Object> new_object;
   Handle<Object> trap_args[] = {target, arg_array, new_target};
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, new_object,
       Execution::Call(isolate, trap, handler, arraysize(trap_args), trap_args));
   // 9. If Type(newObj) is not Object, throw a TypeError exception.
   if (!new_object->IsJSReceiver()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate,
-        NewTypeError(MessageTemplate::kProxyTrapConstructMustReturnObject,
-                     new_object));
+        NewTypeError(MessageTemplate::kProxyConstructNonObject, new_object));
   }
   // 10. Return newObj.
   return *new_object;
 }
 
 
 RUNTIME_FUNCTION(Runtime_IsJSProxy) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Object, obj, 0);
@@ skipping 12 matching lines @@
 RUNTIME_FUNCTION(Runtime_RevokeProxy) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSProxy, proxy, 0);
   JSProxy::Revoke(proxy);
   return isolate->heap()->undefined_value();
 }
 
 }  // namespace internal
 }  // namespace v8