A web-platform-test test [0] overflows the buffer, but then immediately increases the size of the buffer to make room for the new entries. In that case, a `resourcetimingbufferfull` event should never actually fire. In the test, resources/empty.js?xhr2 and resources/empty.js?xhr3 overflow the buffer. Which queues a task (async) to run the "fire a buffer full event" steps. Then the developer calls `setResourceTimingBufferSize()` to make more room. When the "fire a buffer full event" steps do run, "can add resource timing entry" will return true (which means we don't fire `resourcetimingbufferfull`). At that point, both entries of the secondary buffer fit into the primary buffer. [0] https://wpt.fyi/results/resource-timing/buffer-full-then-increased.html?label=experimental