Do not eagerly convert exception to string when creating a message object

src/messages.h

 // Copyright 2006-2008 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.
 
 // The infrastructure used for (localized) message reporting in V8.
 //
 // Note: there's a big unresolved issue about ownership of the data
 // structures used by this framework.
 
 #ifndef V8_MESSAGES_H_
@@ skipping 418 matching lines @@
 // of message listeners registered in an environment
 class MessageHandler {
  public:
   // Returns a message object for the API to use.
   static Handle<JSMessageObject> MakeMessageObject(
       Isolate* isolate, MessageTemplate::Template type, MessageLocation* loc,
       Handle<Object> argument, Handle<JSArray> stack_frames);
 
   // Report a formatted message (needs JS allocation).
   static void ReportMessage(Isolate* isolate, MessageLocation* loc,
-                            Handle<Object> message);
+                            Handle<JSMessageObject> message);
 
   static void DefaultMessageReport(Isolate* isolate, const MessageLocation* loc,
                                    Handle<Object> message_obj);
   static Handle<String> GetMessage(Isolate* isolate, Handle<Object> data);
   static SmartArrayPointer<char> GetLocalizedMessage(Isolate* isolate,
                                                      Handle<Object> data);
 };
 } }  // namespace v8::internal
 
 #endif  // V8_MESSAGES_H_