What is WebKitPluginHost?

I’ve noticed a process taking up a fair amount of memory on my Mac mini, running Snow Leopard: WebKitPluginHost. WebKit is Apple’s HTML rendering engine; it’s used by Safari, Mail (for HTML messages), and many other programs that display HTML pages. But I never noticed it before as a process. In addition, it’s currently taking up more that 200 MB of real memory. Does anyone know what this is?

Follow-up: interestingly, though not surprisingly, the process disappeared after quitting Safari. I think I figured out where it came from: I was uploading a file to my MobileMe iDisk when I noticed it. Perhaps that “PluginHost” is something that is needed by the special window that displays when you make an upload. I’m surprised that it used so much RAM, but I was uploading a file that was around 190 MB. Maybe it takes up RAM corresponding to the size of the upload… More testing will be needed.

Follow-up: it’s a process used when certain plugins are called by WebKit, including the Flash Player plugin.