[Cross-posted to dev.planning, followups to dev.platforms.mobile please]
After substantial discussion, we have decided to build future versions
of Firefox on Android with a native UI instead of the current XUL
implementation. The team is already working on this project on the birch
branch , and we are tracking the early work on the wiki.  To be
clear, we're still building on Gecko. This change is just about the way
we build our UI.
There are several reasons for making this change, most notably:
* Startup - A native UI can be presented much faster than a XUL based
UI, since it can happen in parallel with Gecko startup. This means
startup times in fractions of a second, versus several seconds for a XUL
UI on some phones.
* Memory use - We believe a native UI will use significantly less memory
* Responsiveness - A native UI has the potential for beautiful panning
and zooming performance
Firefox on Android is a critical part of supporting the open web, and
this decision puts us in a position to build the best Firefox possible.
It's still early days, so we have a lot of questions to answer. We’re
talking with the Add-on SDK team about the best way to support
extensions. We’re talking with l10n about how to ensure we support
Firefox users wherever they live around the world.
Next week, the team is meeting in Toronto to break down this work and
prioritize it. We'll be on IRC in #mobile if you want to get involved,
and pushing updates to the repo regularly. By the end of next week, we
will have a clearer outline of the work ahead, and we'll update this
list with those details.
It's too early for us to determine when this work will be ready for
users, but we are certain that it will not impact the versions currently
on the Beta and Aurora channels. Firefox 8 and 9 will ship with the XUL
UI, including the new UI for tablets, while we build the native UI.
Director of Firefox Engineering