Här är lösningen för er som tycker det är intressant
http://howto.cnet.com/8301-11310_39-57600794-285/return-to-youtubes-old-way-of-buffering-full-videos/
och nedan ifall sidan försvinner
Dom som gjort Extension "Youtube Center"
https://github.com/YePpHa/YouTubeCenter/wiki
YouTube Center installs a small settings button in the upper-right corner of YouTube. Click on the gear icon to open the settings panel, which conveniently opens over your current YouTube page. It lets you tweak oodles of settings, but for the purposes of this post, you'll need to click on the Player tab at the top and then uncheck the box for Dash Playback. No need to save; just click the X in the upper-right corner to close the settings window and return to your YouTubing ways.