This patch disables device sensors except orientation by default.
It implements per-sensor prefs to disable orientation, motion, proximity and ambient light
selectively. The patch also makes the pref checks happen at runtime (versus on process
start) using Preferences::AddBoolVarCache.
The patch also removes the related Event constructors also.
MozReview-Commit-ID: EA8ARjjtlkF
--HG--
rename : dom/events/test/test_bug742376.html => dom/events/test/test_deviceSensor.html
rename : dom/events/test/test_eventctors.html => dom/events/test/test_disabled_events.html
rename : dom/events/test/test_eventctors.html => dom/events/test/test_eventctors_sensors.html
extra : rebase_source : 39da98ac9226ac727f5197d28561b0b762da06f4
