layer at (0,0) size 800x600
  RenderView at (0,0) size 800x600
layer at (0,0) size 800x600
  RenderSVGRoot {svg} at (0,100) size 800x100
    RenderSVGResourceMasker {mask} [id="Mask"] [maskUnits=userSpaceOnUse] [maskContentUnits=userSpaceOnUse]
      RenderSVGRect {rect} at (0,0) size 800x300 [fill={[type=SOLID] [color=#FF0000]}] [x=0.00] [y=0.00] [width=800.00] [height=300.00]
    RenderSVGContainer {g} at (0,100) size 800x100
      RenderSVGRect {rect} at (0,100) size 800x100 [fill={[type=SOLID] [color=#0000FF]}] [x=0.00] [y=100.00] [width=800.00] [height=100.00]
        [masker="Mask"] RenderSVGResourceMasker {mask} at (0,0) size 800x300