849 prep fill area cleanup

@doutriaux1 @aashish24 

Had an hour to kill and took a stab at optimizing the vcs scalar bar implementation. Ended up cutting the time down from 0.262s to 0.89s on my machine.

Ref #849 
If having different lengths of x/y are supported, then yes, we should revert it. But otherwise, padding out the arrays with the last value will mask errors and produce invalid results, rather than let the user know something went wrong.

I'm not sure what you mean by removing the lines that create the points, which lines are you referring to?