Ok after hours I finally got it to work but it took additional steps not mentioned in the initial post I had to jump around to find enough info. I was having trouble viewing particular html5/h.264 videos and the like on firefox portable 48.0, test pages showed negative for h.264 support. First I tried the latest FF portable 52.2.1ESR but still no joy. Since I run a portable version of firefox 48.0 I made a mirror copy of that to alter in case I messed up. BTW I'm running winxp 32 w/sp3
First I added the files into my FF profile folder as described on post 1.
Then I added/edited these 9 lines in about:config as described.
media.gmp-eme-adobe.enabled (boolean, true)
media.gmp-eme-adobe.forceSupported (boolean, true; FF 49.0+)
media.gmp-eme-adobe.forcevisible (boolean, true; FF 45-48, no longer used in 49.0+)
media.gmp-eme-adobe.visible (boolean, true; FF 49.0+)
media.gmp-eme-adobe.version (string, 17; required for manual install now that automatic install is no longer an option)
media.gmp-eme-adobe.abi (string, x86-msvc-x86; not required, you can set it if you want to more closely mimic automatic install)
media.gmp-eme-adobe.lastUpdate (integer, 1500000000; not required, you can set it if you want to more closely mimic automatic install)
media.gmp.decoder.enabled (boolean, true)
media.eme.enabled (boolean, true; defaults to false if you downloaded a DRM-free version of FF
SO after all this nothing changed so I went further into the thread and found these additions, I'm not sure if one or all of them made the difference.
I opened add-ons and right-clicked the primetime content encryption plug-in and selected find update, I think it does something but I'm not positive.
BACK to about:config
I rechecked all my added and changed lines, it seemed one or more were missing or not true ect. I'm not sure if this was my fault or not.
checked media.gmp-manager.url I had to simply replace the %VERSION% part in the long url with 48.0, of course you will put in which ever version you have.
I opened add-ons and right-clicked primetime content encryption and selected find update again. I rebooted and my videos played! Thanks gang.