Changes

# <strike>Save the screenX and screenY position before locking the mouse.</strike> - humph

# <strike>Reset the mouse position back to the original position when unlocking.</strike> - humph

# "When unlocked, the system cursor can exit and re-enter the user agent window. If it does so and the user agent was not the target of operating system mouse move events then the most recent mouse position will be unknown to the user agent and movementX/Y can not be computed and must be set to zero"

# Trying to lock a locked element should fire the success callback diogogmt

# User agents may prompt for confirmation before locking, this preference may be saved as a content setting (Mentioned in class by humphd, setting would be in about:config ) mjschranz

# Do we need to add a user pref to enable/disable mouse lock? Nice to have, not blocking. - northwind

====Tests====