Tweaks for timeline dragging code.
Tweaks for timeline dragging code.

Keep the drag going if the mouse leaves the timeline.  Prevent the
default to disable the browser selection code from happening.

ujdhesa/unisubs,ujdhesa/unisubs,ujdhesa/unisubs,eloquence/unisubs,ReachingOut/unisubs,ujdhesa/unisubs,pculture/unisubs,ReachingOut/unisubs,ofer43211/unisubs,pculture/unisubs,eloquence/unisubs,norayr/unisubs,ofer43211/unisubs,wevoice/wesub,wevoice/wesub,norayr/unisubs,norayr/unisubs,pculture/unisubs,pculture/unisubs,ofer43211/unisubs,eloquence/unisubs,eloquence/unisubs,ReachingOut/unisubs,ReachingOut/unisubs,ofer43211/unisubs,norayr/unisubs,wevoice/wesub,wevoice/wesub