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

A
B
C
layer at (0,0) size 31x20
  LayoutNGBlockFlow (positioned) {DIV} at (8,50) size 31x20
    LayoutFlexibleBox {SELECT} at (0,0) size 31x20 [bgcolor=#DDDDDD] [border: (1px solid #767676)]
    LayoutText {#text} at (0,0) size 0x0
layer at (5,1) size 9x18
  LayoutBlockFlow {DIV} at (5,1) size 9x18
    LayoutText {#text} at (0,1) size 9x16
      text run at (0,1) width 9: "C"