Article title shifts when creating a new article on Firefox for Mac

[joshpc]

Describe the bug
In Firefox for Mac, the Article Title will shift once you enter a title.

This occurs because we estimate what the height of the scrollView will be if it had a line using the font's lineHeight property. This is an approximation; scrollViews don't have to respect this. Chrome and Safari does, generally, but Firefox does not.

This results in the content shifting down just a little.

To Reproduce
Using Firefox

Steps to reproduce the behaviour:

1. Create an article.
2. Type a title

Expected behaviour
The content should not shift.

Browser and Device (please complete the following information):

• Firefox, Mac