Description:

When trying to sample music on Amazon, the play buttons cannot be selected to initiate playback. On Chromium, it works, however.

Additional info:
firefox-31.0-1 x86_64

Here is a sample page to try that illustrates the problem:
http://www.amazon.com/gp/product/B00LBUMNDK/ref=s9_simh_gw_p340_d0_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-2&pf_rd_r=01FPEP648ET3HJT7Z0RV&pf_rd_t=101&pf_rd_p=1688200382&pf_rd_i=507846

Steps to reproduce:
Navigate to a page that has mp3 samples and try to listen to them.

Actual results:
The button is dead.

Expected results:
Playback should commence.

This has not been working for a few weeks, but it used to work. I cannot indicate when, exactly, the error was introduced.