Page stalls say where the window was

Obeya's stall log records when a page freezes. Long freezes with no stated cause turned out to come only while nobody was at the screen: display off, screen locked, or the user idle. Each page stall in the log now names the browser, whether its window was in use and when the page was last used. In Safari, the Obeya app and Firefox, which say nothing about where a page's time went, a window in the background no longer logs stalls, so the log keeps to freezes someone could have noticed.