[gcp]

Download it directly from the Mozilla site: http://www.mozilla.org/en-US/mobile/aurora/

The Ace has very little available memory, so Mozilla still blocks it for Beta & Release because they think it doesn't work well enough. But your mileage may vary (greatly).

This is the Aurora build (Firefox 21) which has some more optimizations.

Chrome can't run on a phone that doesn't have at least Ice Cream Sandwich (Android 4.0+) AFAIK.