Had trouble compiling but found there was a dependency missing to mesia or at least mesia development tools. Emerging mesia-progs before xulrunner fixed the issue (clearly stated in the logs from xulrunner I must say but nevertheless). Please tell me where to post this if this is not appropriate. Thanks. Reproducible: Always Steps to Reproduce: 1. blank system (new install in my case) 2. emerge gnome 3. halts on xulrunner fixed by emerging mesia-progs before resuming. note; system is built with ACCEPT_KEYWORDS ~amd64
Other than that your solution was almost certainly wrong, you've failed to provide the log of the failure.
No logs to get any longer I am afraid, but the solution worked :) Do what you like ...