Bug 16269: add-on compatibility check occurs repeatedly
Bug 16269: add-on compatibility check occurs repeatedly

Ensure that update-related browser preferences are written to
disk by flushing them during startup.

wyuelin/mymeek,infinity0/meek,gorshell/forkmeek,projectarkc/meek,infinity0/meek,wyuelin/mymeek,infinity0/meek,projectarkc/meek,gorshell/forkmeek,infinity0/meek,projectarkc/meek,projectarkc/meek,projectarkc/meek,infinity0/meek,wyuelin/mymeek,gorshell/forkmeek,wyuelin/mymeek,gorshell/forkmeek