So far, we have been downloading xulrunner sdk for the sole purpose of using its xpcshell. At the end most of this big tarball (around 70MB) is unused. Ideally, we would only download an xpcshell package, but that doesn't exists. Instead of having to maintain a new xpcshell package, we could instead download something any usefull for gaia developers. B2g desktop for example. That would allow to run gaia easily as the build system would already have downloaded b2g desktop. We could easily add a run command to open gaia in this desktop environment. That would ease working on gaia with b2g desktop instead of Firefox nightly. Also, we can optionally use that to have a fine control on which gecko revision we should be using with a given gaia revision. Then, we would switch from b2g desktop to Firefox Mulet (bug 943878) as soon as it is ready while trying to enable App manager/simulator features in b2g desktop/firefox mulet runtime. This would only require some tweaks in gaia's Makefile and enable xpcshell in b2g desktop builds.

try to switch to b2g-desktop but got error when use Components.utils.import('resource://gre/modules/osfile.jsm').

It seems to be a b2g specific brekage of osfile, marco has this exact same exception while working on apps for b2g: bug 981085 comment 13 resource://gre/modules/osfile/osfile_unix_allthreads.jsm:2 - TypeError: "toString" is read-only

Yoric, Does that ring any bell to your ears? We are sucessfully able to load'n use OS.File on a 'regular' xpcshell, but not on a 'b2g xpcshell'. The only think I can imagine is something wrong with the global sharing of jsm, but I don't see why it wrong revent toString overloading right here...

Oops, sorry about that. The patch has been ready for some time but unlanded. FWIW, the problem seems to be that, for some reason, `Error` attaches `toString` to the instance, rather than to the prototype. Once the object has gone through `Object.freeze`, fun ensues.

Commented on bug 1014484 too, but this could be bug 980752 that all should feel free to steal.

Firefox OS is not being worked on