Make isolate.h usable without objects-inl.h header.

src/messages.cc

 // Copyright 2011 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/messages.h"
 
 #include "src/api.h"
 #include "src/execution.h"
+#include "src/isolate-inl.h"
 #include "src/string-builder.h"
 
 namespace v8 {
 namespace internal {
 
 
 // If no message listeners have been registered this one is called
 // by default.
 void MessageHandler::DefaultMessageReport(Isolate* isolate,
                                           const MessageLocation* loc,
@@ skipping 453 matching lines @@
   if (obj->IsUndefined()) return default_value;
   if (!obj->IsString()) {
     ASSIGN_RETURN_ON_EXCEPTION(isolate, obj, Object::ToString(isolate, obj),
                                String);
   }
   return Handle<String>::cast(obj);
 }
 
 }  // namespace internal
 }  // namespace v8