I recently found a way to boost performance on the android platform for html 5 based games. There's an alternative browser you can installed called "Dolphin". Its been around for a long time, but has never been as popular as firefox or chrome. They have an addon for it (also in the market) called "Dolphin Jetpack" Which is designed for accelerating HTML5 apps. When you load up a game it asks you if you want to enable "game mode". On my kindle fire, i was getting less than 10 fps on lots of different games, but now i can get over 40 fps on the same game using this method.
The only thing i noticed is that some games didn't work with sound on the kindle fire using this method. Please report back which device you've tried this on and if sound works correctly.
Here are the links to the apps in the appbrain store