UserAgent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:53.0) Gecko/20100101 Firefox/53.0

Steps to reproduce the problem:
1. Activate a screen reader such as NVDA on Windows or VoiceOver on macOS.
2. Visit www.desmos.com/calculator
3. In the first expression, enter "y=sinx".
4. Down-Arrow to focus the next expression, and enter "y=1/2x".
5. Up-Arrow twice to return to the first expression.
6. Down-Arrow back to the second expression.
7. Repeat steps 5 and 6 a few times.

What is the expected behavior?
On both platforms, I hear "expression 1, y equals sin x," and "expression 2, y = start fraction, 1 over 2 x end fraction."

What went wrong?
On Windows, I hear the name of the expression I just left, followed by the name of the expression which gains focus. On Mac, I sometimes hear th name of the expression I am moving to, but usually it is chopped off and VoiceOver says "y/sinx1/2 powered by Desmos."

Did this work before? Yes 57

Chrome version: 58.0.3029.96 (64-bit)  Channel: stable
OS Version: 10.0
Flash Version: NA

This has all the symptoms of two focus events being rapidly sent to the screen reader. Chrome 57, current Firefox, and Safari do not exhibit this issue.