Using chrome, on an about:blank page in the console:

Object.hasOwnProperty(window, "performance") returns false.

Yet, Object.getOwnPropertyNames(window) returns an array containing performance.

Even, Object.getOwnPropertyDescriptor(window, "performance") works and returns {"enumerable": true,"configurable": true}

Im not sure why this is occurring, or how to recreate it. I looked at the Mozilla docs for each of these functions and nothing explained this behavior.