I tried with both an e10s and non-e10s window. It works in chrome

blassey: what is the value of your "shumway.swf.whitelist" pref? The default value is "http://g-ecx.images-amazon.com/*/AiryBasicRenderer*.swf", but if you had previously changed your "shumway.disabled" pref to false, then the Nightly switch to whitelist Shumway just for amazon.com would set "shumway.swf.whitelist" to "*" to avoid disabling Shumway everywhere else. And Shumway doesn't support click-to-play. Yury: is this an accurate description of the Shumway policy? We really need to solve these conflicts with the bundled vs extension Shumway. :)

Yes, it's a pretty accurate description. I don't see the version field is specified. But I tested the latest Nightly/extension, and Shumway can play this video. (The same extension did not work in the release version of Firefox though) Shumway might not work well with click-to-play (see also bug 923527), we hope it will be addressed soon by jsplugins.

the pref's value for me is http://g-ecx.images-amazon.com/*/AiryBasicRenderer*.swf

Shumway is not in-product, and I'm 95% certain reading the bug that this was a Shumway issue.