Fullscreen Flash video only shows 1/4 of video
I've found it. After looking a little further, I was able to find something I missed some time ago.


  
  In the URL bar enter chrome://plugins/
  Locate the Flash plug-in, you should see multiple versions listed
  Click Disable for the plug-in with the location /opt/google/chrome/PepperFlash/libpepflashplayer.so
  You should still have one enabled in another location, like /usr/lib/adobe-flashplugin/libflashplayer.so
  Restart Chrome (quit and open again)
  


Source: https://code.google.com/p/chromium/issues/detail?id=135353#c25

This fixed it for me!