Google Chrome: Search API?
Please note that I am basing my answer off of the context of your question, as at my work I cannot see the image. If my answer is not what you are looking for, please let me know.
I'm not sure if this exactly how Google Chrome does this, but Chrome supports it, and I found this by looking at the source code for this Stack Overflow page.
This is an XML specification for providing custom searching. It is currently supported by Chrome, FF, and IE7.
If you want to look at an example page, this is the link to the Stack Overflow specification: