AccumulatedVisualContext Tree:
  [1] scroll_frame_id=1 (PaintableWithLines(BlockContainer<PRE>#out))
    [2] clip=[28,23 80x70] (PaintableWithLines(BlockContainer<DIV>.clipped))

DisplayList:
SaveLayer@0
  CompositorWheelHitTestTarget@0 target_scroll_frame_index=0 rect=[0,0 800x600]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[0,0 800x21]
  CompositorWheelHitTestTarget@2 target_scroll_frame_index=0 rect=[8,13 150x150]
  FillRect@2 rect=[8,13 150x150] color=rgb(128, 0, 128)
  DrawGlyphRun@2 rect=[8,13 71x18] translation=[8,26.796875] color=rgb(0, 0, 0)
  DrawGlyphRun@2 rect=[8,31 72x18] translation=[8,44.796875] color=rgb(0, 0, 0)
Restore@0