Based on the docs true is equal to {capture: true}
> In older versions of the DOM specification, the third parameter of addEventListener() was a Boolean value indicating whether or not to use capture. Over time, it became clear that more options were needed. Rather than adding more parameters to the function (complicating things enormously when dealing with optional values), the third parameter was changed to an object that can contain various properties defining the values of options to configure the process of removing the event listener.
https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#Improving_scrolling_performance_with_passive_listeners
Inside of Nuclide, we have multiple places where we have multiple icons close together that have a tooltip: the left toolbar, the bottom status bar, the debugger icons...
The current behavior is very frustrating as you've got to wait for the delay on every single one of them. But, we have a clear signal that the user wants a tooltip when s/he waits the time to see it and it's likely that moving the mouse over the next item quickly means that s/he wants to see it as well.
This pull request introduces the concept of follow through: if you have seen a tooltip, you're going to instantly see tooltip on the next element you mouse over within a short timer (300ms right now).
Test Plan:
Video before:

Video after:

Released under CC0