The evidence that development has stalled is the fact that the tree for landing code changes has closed. SPDY, recently announced here, has been, or is being considered for, removal to relieve code size.
These are slightly sensationalist ways of phrasing the following facts:
* libxul hit linker limits on 32-bit Windows builds with profile guided optimization enabled, as it did a couple of years ago. PGO uses a lot of memory, but it's how we deliver on Windows, so it's important.
* mozilla-central and mozilla-inbound were temporarily closed to avoid further build failures whilst the issue was explored. Other trees (try, services-central, etc. etc. etc.) remained open.
* some recent large changes to libxul were backed out in order to relieve pressure on linking.
* mozilla-central is now open for landings that aren't libxul-related, apart from those to trim it down. JavaScript and other landings continue unabated.
See Bugzilla for the full scoop.