Bug 1363421 - Part 2, delay the initialization of UserAgentOverrides.jsm until first nsHttpChannel is created. r=mcmanus UAOverridesBootstrapper.js is introduced to delay the initialization of UserAgentOverrides.jsm until the creation of the first nsHttpChannel. Uninit will be triggered at profile-change-net-teardown because no network traffice after this point. MozReview-Commit-ID: F8Lpn6RyZEm

[flake8]
# See http://pep8.readthedocs.io/en/latest/intro.html#configuration
ignore = E121, E123, E126, E129, E133, E226, E241, E242, E704, W503, E402
max-line-length = 99
filename = *.py, +.lint