The Performance panel would reveal critical issues in this code: 1) It would show repeated layout thrashing caused by alternating reads and writes to the DOM, 2) Each innerHTML += operation forces a complete reparse and rerender of the element's contents, 3) The flame chart would display numerous layout recalculations and rendering operations, 4) The timeline would show excessive CPU usage during this loop, 5) Performance recordings would quantify exactly how much time is spent in layout and rendering, 6) It would highlight the forced synchronous layouts triggered by each iteration, 7) The panel would provide metrics showing the impact on frame rate and responsiveness, 8) This information would guide optimization by revealing the need to batch DOM updates or use more efficient approaches like DocumentFragment.