AccumulatedVisualContext Tree:
  [0] transform=[1,0,0,1,0,0] origin=(0,0) (ViewportPaintable(Viewport<#document>))
    [1] scroll_frame_id=1 (PaintableWithLines(BlockContainer<PRE>#out))

DisplayList:
SaveLayer@0
  CompositorWheelHitTestTarget@0 target_scroll_frame_index=0 rect=[0,0 800x600]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[0,0 800x321]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 784x300]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 300x300]
  FillRect@1 rect=[8,8 300x300] color=rgb(211, 211, 211)
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 100x100]
  FillRect@1 rect=[8,8 100x100] color=rgb(173, 216, 230)
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[13,13 100x100]
  FillRect@1 rect=[13,13 100x100] color=rgb(255, 127, 80)
  DrawGlyphRun@1 rect=[13,13 65x16] translation=[13,25.796875] color=rgb(0, 0, 0)
Restore@0