In any case since extensions are separate processes I am more perplexed as to how you are getting that low memory usage for the VIM tab. Make sure you wait for the page to load - it takes some time for me to start reaching 900Mb levels and the tab is still loading at that point.
I waited the first time. If I scroll to the bottom of the page I get 98,232 KB. Highest I can get now. Task Manager says close to the same thing, and my computer isn't under memory pressure so I don't expect Windows to have paged out a bunch of Chrome's memory.
http://imgur.com/im0YFhw - 1.6GB on 64-bit build. I get 107Mb in an incognito tab as well. That has got to be a bug - more than 10 times mem usage on regular tab!
