@arikon 
"What triggers a reflow or a repaint:
Anything that changes input information used to construct the rendering tree can cause a repaint or a reflow, for example:
Adding, removing, updating DOM nodes
Hiding a DOM node with display: none (reflow and repaint) or visibility: hidden (repaint only, because no geometry changes)
Moving, animating a DOM node on the page
Adding a stylesheet, tweaking style properties
User action such as resizing the window, changing the font size, or (oh, OMG, no!) scrolling"
http://www.phpied.com/rendering-repaint-reflowrelayout-restyle/

По идее, так как мы не меняем DOM-дерево, не изменяем отображение DOM-элементов и свойства в CSS не трогаем, то не должно быть reflow + repaint.