R1:49b03c03531f

Improve tooltip behavior for Application menu items

Summary:
Ref T12174.

- Fix text antialiasing pop-in at the end of the animation in Safari.
- Fix flickery animation replay when mousing inside a tooltip element, or rapidly switching between tooltip elements.
- To accomplish this: don't play the animation if the last tip was hidden less than 500ms ago.

Test Plan:
- Viewed a tooltip in Safari.
- Waved cursor wildly over application items, both left-right (within an item) and up-down (between…