Javascript to retrieve pagetext of chrome extension plugin?

I've had success using this to retrieve the page text of pages on a couple different websites, but I'm trying to retrieve the page text of a chrome extension plugin.

This is the extension I'm referring too.

Is it possible to pull the pagetext of this? I'm guessing I have to alter the parentnode portion?

If it matters the overall goal of this is to set it to a variable to search with regex.

I can provide some html if guided.