AccumulatedVisualContext Tree:
  [1] scroll_frame_id=1 (PaintableWithLines(BlockContainer<PRE>#out))
    [2] transform=[0.9659258,-0.25881904,0.25881904,0.9659258,0,0] origin=(38,38) (PaintableWithLines(BlockContainer<DIV>.box.a))
    [3] transform=[1.1,0,0,1.1,0,0] origin=(103,38) (PaintableWithLines(BlockContainer<DIV>.box.b))
    [4] transform=[1,0.17632698,0,1,0,0] origin=(168,38) (PaintableWithLines(BlockContainer<DIV>.box.c))

DisplayList:
SaveLayer@0
  CompositorWheelHitTestTarget@0 target_scroll_frame_index=0 rect=[0,0 800x600]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[0,0 800x81]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 784x60]
  CompositorWheelHitTestTarget@1 target_scroll_frame_index=0 rect=[8,8 784x60]
  CompositorWheelHitTestTarget@2 target_scroll_frame_index=0 rect=[8,8 60x60]
  FillRect@2 rect=[8,8 60x60] color=rgb(255, 0, 0)
  DrawGlyphRun@2 rect=[8,8 7x18] translation=[8,21.796875] color=rgb(0, 0, 0)
  CompositorWheelHitTestTarget@3 target_scroll_frame_index=0 rect=[73,8 60x60]
  FillRect@3 rect=[73,8 60x60] color=rgb(0, 128, 0)
  DrawGlyphRun@3 rect=[73,8 9x18] translation=[73,21.796875] color=rgb(0, 0, 0)
  CompositorWheelHitTestTarget@4 target_scroll_frame_index=0 rect=[138,8 60x60]
  FillRect@4 rect=[138,8 60x60] color=rgb(0, 0, 255)
  DrawGlyphRun@4 rect=[138,8 10x18] translation=[138,21.796875] color=rgb(0, 0, 0)
Restore@0