Why not implement the class yourself?
You really shouldn't. Ideally, the URLRequestContext shouldn't need to know about how it was created. You should instead figure out how to access the ChromeURLRequestContextGetter from wherever you are, or pass it down somehow.
Then it can mot meet my needs. Since it has to change URLRequest interface by adding Getter variable to pass down, then by just replacing net.dll the existing chrome cannot run properly. There is going to be runtime crash except recompile the whole chrome. My purpose is not to replace the whole chrome.