add comments to introduce the needsRender element of the renderReusingNode path

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>
remove unnecessary code

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>
don't handle scroll events when the work for layout has already been done

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>
remove unnecessary overhead caused by looking of size when we already know it

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>