The launcher row's `on_click` selects the tab. Its child close glyph
also has its own `on_click` that selects + closes. After the close,
the click bubbled up to the row, which then tried to re-select the
tab we just removed — usually a no-op but a wasted state churn that
can race with the close in BrowserCore.
Add `cx.stop_propagation()` after the close handler so the click
ends at the close glyph.
ZacharyZhang-NY
adb278b3bb