Chrome Version: M58 beta, but happens back to M56
macOS10.2.x

0) start with a window with a bunch of existing tabs
1) open a new window
2) drag its tab and over over first window with a lot of tabs but don't release mouse
3) move back and forth over tab strip

expected:
- as mouse moves back and forth, tabs in window move out of the way so drop point is immediately obvious while mouse is moving

actual:
- drop feedback only updates when mouse stops moving

This is a regression and we should fix it for M58 stable.