Bug 913848: Attempt to fix intermittent test_unix_domain.js timeout with MOAR ASYNC. r=mayhemer

This patch makes the tests avoid expecting data from the client to be
available to the server immediately upon accepting a connection; instead,
the server uses asyncWait to receive those first bytes. This changes both
test_echo and test_connect_permission.

I've pushed this through the try server twice, and it didn't hang. In
either case, it adds a few more do_prints to give me more clues about the
source of the problem.
Bug 914601 - Remove non-required, crashing-on-oom assert in GlobalObject::getIntrinsicValue. r=terrence

--HG--
extra : rebase_source : cb1d3e8f40e0b0264214a1c151adf1e6aeacd622
Bug 912874 - New API to enumerate mutation observers, r=peterv

--HG--
extra : rebase_source : a11135f5fbf0faec36fd2cf5a3f1d348886d0bdc
Bug 914498 - Minimize the #includes in accessible/src/base; r=tbsaunde
Display fill ratio when showing FPS counter (bug 915342, r=bgirard).