If impossible to modify header in JSONP. How does twitter extension in Chrome work?

问题

Now I'm working to do twitter client with Javascript.
After I read this topic, I have question

Modify HTTP Headers for a JSONP request

He told impossible way to modify HTTP Header when using JSONP.
If it's true. How does twitter extension work in Chrome ?
I think Chrome extension use Javascript, too.

回答1:

Extensions have more privileges then "normal" JavaScript code executing within a page. Check here:

• http://code.google.com/chrome/extensions/xhr.html

来源：https://stackoverflow.com/questions/4273182/if-impossible-to-modify-header-in-jsonp-how-does-twitter-extension-in-chrome-wo