Debugging #17931, by printing all parts of the event lifecycle including
timestamps, uncovered that some events for which a timeout was logged
actually did get triggered correctly in the browser. Going over the code
and discovering https://stackoverflow.com/questions/47107465/puppeteer-how-to-listen-to-object-events#comment117661238_65534026
showed what went wrong: if the event we wait for is triggered then
`Promise.race` resolves, but that doesn't automatically cancel the
timeout. The tests didn't fail on this because `Promise.race` resolved
correctly, but slightly later once the timeout was reached we would see
spurious log lines about timeouts for the already-triggered events.
This commit fixes the issue by canceling the timeout if the event we're
waiting for has triggered.
51dcd6a1ba