Output area height is rounded when fixing height on clear

[jasongrout]

In

notebook/notebook/static/notebook/js/outputarea.js

Line 969 in 5192d72

var height = this.element.height();

, we use jquery to find and fix the height of an output area in order to prevent jumpiness when clearing an output area. However, the jquery .height() function rounds the height to the nearest integer, which causes some jitter. It would be better to use .getBoundingClientRect().height, which doesn't round the height.

[jasongrout]

@gnestor - is it too late for me to put in a quick PR for this before 5.1?

[gnestor]

No, go ahead, I'm still working through some remaining issues 👍