PLEASE, TSO change technologies to HTML5, even Java, the latest release of Firefox (version 54) now has major lagging issues with Flash 26. After a few weeks with on the Mozilla team explaining about TSO and how it uses flash. I get the feeling they are "moving on" from flash. That only leaves Chrom(ium) and Opera.
The response from the Mozilla Bug team:
The probable cause of this is that we forced all Flash elements into windowless
mode on Linux. This is a tradeoff we made to support multi-process browsing,
and makes the browser faster in general but causes painting slowness for large
Flash elements/games.
Given the declining state of Flash, Mozilla isn't going to dedicate a lot of
engineering resources to this (P5). I'll leave this open in case somebody comes
along and wants to do profiling and identify a problem we can fix.
I did ask if "windowless" can be disabled but sadly its hard coded into the browser.