[Extensions] Don't allow gin::Define to be overridden

extensions/renderer/v8_helpers.h

Index: extensions/renderer/v8_helpers.h
diff --git a/extensions/renderer/v8_helpers.h b/extensions/renderer/v8_helpers.h
index 2bfeee8a6f3d73909da77a66b5aca5389e48adc2..1a092aac85eece509f5fff4b91f7fe15dfcc44f1 100644
--- a/extensions/renderer/v8_helpers.h
+++ b/extensions/renderer/v8_helpers.h
@@ -56,12 +56,13 @@ inline bool IsEmptyOrUndefied(v8::Local<v8::Value> value) {
   return value.IsEmpty() || value->IsUndefined();
 }
 
-// SetProperty() family wraps V8::Object::Set(). Returns true on success.
+// SetProperty() family wraps V8::Object::DefineOwnProperty().
+// Returns true on success.
 inline bool SetProperty(v8::Local<v8::Context> context,
                         v8::Local<v8::Object> object,
-                        v8::Local<v8::Value> key,
+                        v8::Local<v8::String> key,
                         v8::Local<v8::Value> value) {
-  return IsTrue(object->Set(context, key, value));
+  return IsTrue(object->DefineOwnProperty(context, key, value));
 }
 
 inline bool SetProperty(v8::Local<v8::Context> context,