I believe it becomes the app's name in the app's title bar on Windows and Linux. I can't double-check right now (don't have access to either), but this was the case before. However, this line is still unnecessary here :), because we already set the right `document.title` in the HTML. The line was meaningful back in the old days when we had two versions of the UI, Polymer and non-Polymer, and they set different titles to be more easily distinguishable. I'll remove the line.