Tighten OpenHandle's extra checks.

src/accessors.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 849 matching lines @@
   info.GetReturnValue().Set(Utils::ToLocal(result));
 }
 
 
 void Accessors::FunctionPrototypeSetter(
     v8::Local<v8::String> name,
     v8::Local<v8::Value> val,
     const v8::PropertyCallbackInfo<void>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<JSObject> object = Utils::OpenHandle(*info.This());
+  Handle<JSObject> object =
+      Handle<JSObject>::cast(Utils::OpenHandle(*info.This()));
   Handle<Object> value = Utils::OpenHandle(*val);
 
   SetFunctionPrototype(isolate, object, value);
 }
 
 
 Handle<AccessorInfo> Accessors::FunctionPrototypeInfo(
       Isolate* isolate, PropertyAttributes attributes) {
   return MakeAccessor(isolate,
                       isolate->factory()->prototype_string(),
@@ skipping 380 matching lines @@
   info->set_data(Smi::FromInt(index));
   Handle<Object> getter = v8::FromCData(isolate, &ModuleGetExport);
   Handle<Object> setter = v8::FromCData(isolate, &ModuleSetExport);
   info->set_getter(*getter);
   if (!(attributes & ReadOnly)) info->set_setter(*setter);
   return info;
 }
 
 
 } }  // namespace v8::internal