[Affected versions]: - 60.0a1 (2018-02-15) - 59.0b10 build3 (20180215111455) [Affected platforms]: - Ubuntu 16.04 x64 [Steps to reproduce]: 1. Launch Firefox. 2. Open a new tab. 3. Drag a Top Site to a corner position and then release it. 4. Drag a Top Site outside the Top Sites area and then release it. [Expected result]: - [step3], [step4] The animation is fast and smooth when the top site is moved back to its original position. [Actual result]: - [step3], [step4] The animation is slow when the top site is moved back to its original position (see the screencast https://goo.gl/3G4YNJ) [Regression range]: - This is not a regression as it is reproducible all the way back to 59.0a1 (2017-12-22), when bug 1402192 was implemented.

This looks like default platform behavior. Maybe we should get UX feedback if we want to change it.

Is this specifically related to drag-n-drop? I seem to get the same drag-cancel / return to original animation speed for 60 with drag and 58 without.

(In reply to Ed Lee :Mardak from comment #2) > Created attachment 8951715 [details] > video 60 vs 58 > > Is this specifically related to drag-n-drop? I seem to get the same > drag-cancel / return to original animation speed for 60 with drag and 58 > without. Yes, indeed, this seems to also affect the past builds behaviour (the ones without drag-n-drop).

Sounds like this is intended os behavior.