Tests <select> text update when popup is visible and selectionIndex changes.
Needs run-layout-test.

layer at (0,0) size 33x20 116x20 backgroundClip at (8,50) size 33x20 116x20 clip at (8,50) size 33x20 116x20
  LayoutBlockFlow (positioned) {DIV} at (8,50) size 33x20 116x20
    LayoutMenuList {SELECT} at (0,0) size 33x20 116x20 [bgcolor=#C0C0C0] [border: (1px solid #A9A9A9)]
      LayoutBlockFlow (anonymous) at (1,1) size 31x18 114x18
        LayoutText (anonymous) at (4,1) size 9x16
          text run at (4,1) width 9: "C"
    LayoutText {#text} at (0,0) size 0x0