Try to avoid excessive redraws.

Most of them seem to be caused by using :hi statements, although the
highlighting group to be created is exactly the same. Therefore, get the
info from actual definition and only execute :hi when the new group is
actually different.

Also try to avoid to generate :hi statements when the popupmen is
visible. This causes flickers.

autoload/airline/extensions/tabline.vim

@@ -59,6 +59,9 @@ function! s:update_tabline()
 endfunction
 
 function! airline#extensions#tabline#load_theme(palette)
+  if pumvisible()
+    return
+  endif
   let colors    = get(a:palette, 'tabline', {})
   let l:tab     = get(colors, 'airline_tab', a:palette.normal.airline_b)
   let l:tabsel  = get(colors, 'airline_tabsel', a:palette.normal.airline_a)