This is a great use of Chromium! Storytime! When we started designing Chrome back in 2006, and despite having spent the past year working on Google's Firefox team, my favorite browser was iRider, which was an IE shell with tree-style-tabs. It was too power-user for what we were going for, but some of the concepts (pinning) live on in Chrome today.
Chrome might as well support the Sidebar API to make this possible like Firefox will do with Tree-Tab-Style Add-on iirc. I read a bug report once at the Chromium bug tracker saying roughly "Sidebar API wont be implemented because UI needs to stay simple".