AccumulatedVisualContext Tree:
  [1] scroll_frame_id=1 (PaintableWithLines(BlockContainer<PRE>#out))
    [2] transform=[1,0,0,1,50,30] origin=(58,58) (PaintableWithLines(BlockContainer<DIV>.box))

DisplayList:
SaveLayer@0
  CompositorWheelHitTestTarget@0 target_scroll_frame_index=0 rect=[0,0 800x600]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[0,0 800x121]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 784x100]
  CompositorWheelHitTestTarget@2 target_scroll_frame_index=0 rect=[8,8 100x100]
  FillRect@2 rect=[8,8 100x100] color=rgb(0, 0, 255)
  DrawGlyphRun@2 rect=[8,8 38x18] translation=[8,21.796875] color=rgb(0, 0, 0)
Restore@0