How long the primary may stay silent before the worker fails over to the
freshest other port. Pongs are posted from the page's message handler,
which runs even in background-throttled tabs, so silence this long means
the tab is frozen, crashed or gone — not merely backgrounded.
How long the primary may stay silent before the worker fails over to the freshest other port. Pongs are posted from the page's message handler, which runs even in background-throttled tabs, so silence this long means the tab is frozen, crashed or gone — not merely backgrounded.