This allows us to fire MozMouseHittest events from tests and then read
the hittest result from the compositor APZTestData. The MozMouseHittest
event was chosen in particular because the existing uses of it are
similar in nature - it is a dummy event that is used to determine what
elements a particular coordinate targets. It is also an event that is
never generated by the OS and so using this event gives us more control
over what ends up in the APZTestData.
MozReview-Commit-ID: KHjIX7EpK2A
--HG--
extra : rebase_source : f7d7d729c1935eefd49ed06d8644ff9ef537f2e1
Boris Zbarsky
Kartikaya Gupta
Mason Chang
Botond Ballo