Problems drawing left/right arrow in mover

[NSoiffer]

Issue Summary

MathJax has some problems with drawing a stretchy arrow as detailed below. The results differ between Chrome and Firefox, but in all cases, the arrow display in an mover has problems.

Steps to Reproduce:

1. View the codepen I created

2. In Firefox, the right arrow is not stretched in normal display -- it is right aligned; the left arrow is left aligned (maybe the horizontal line part isn't visible?). When zoomed, the pieces don't align. The alignment problem might be the same issue reported in mathjax 3.0 and \overrightarrow #2226. Here is a screen shot:
   
   I tried different zoom factors. The alignment problems shows up at 150%, 200%, 300%, but not at 400%.

3. In Chrome, do the same thing. The display is better, but the unzoomed right arrow has different widths for the pieces. In the zoomed case, it is just barely wrong -- an extra pixel is highlighted where the pieces are joined.
   

Version:

[dpvc]

I'm going through back issues, and just saw that I never responded to this. (I was just starting remote classes, and was swamped at the time.) I will look into it further.