Scroll delay in Firefox when scroll direction is immediately changed

[bashmish]

Description

The iron-dropdown element while scrolling in Firefox has a delay when the scroll direction is immediately changed in the bottom (or in the top) of the element. The same is true when you use Polymer.IronDropdownScrollManager for other elements.

Expected outcome

It scrolls smoothly when you scroll it up and down.

Actual outcome

It has a noticable delay and then immediately scrolls.

Live Demo

Unordered list https://www.webcomponents.org/element/PolymerElements/iron-dropdown/demo/demo/index.html or any other scrollable iron-dropdown

Steps to reproduce

1. Scroll to the bottom.
2. immediately change the scroll direction and scroll to the top.
3. Notice the delay and after that the scroll position is somewhere to the top.

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10

Not sure about IE and Edge.

[valdrinkoshi]

Tested the wheelEvent.preventDefault() technique on FF w/o polymer, and I can still face this issue http://jsbin.com/negelu/1/edit?html,output
Not sure how to fix this... 😕