Chrome Version: Version 67.0.3381.0
OS: macOS 10.12.6

What steps will reproduce the problem?
(1) Enable chrome://flags/#views-browser-windows
(2) Open two tabs in a window
(3) Drag a tab out of the window
(4) Drag it back into the window

What is the expected result?
Steps 3 and 4 should be smooth as in Cocoa Mode.

What happens instead?
Steps 3 and 4 are not smooth as in Cocoa Mode.