Some fast/canvas tests fail under MacOS

The following fast/canvas tests fail under MacOS:
fast/canvas/2d.text.draw.fill.maxWidth.negative.html
fast/canvas/2d.text.draw.fill.maxWidth.veryLarge.html
fast/canvas/2d.text.draw.fill.maxWidth.verySmall.html
fast/canvas/canvas-arc-zero-lineto.html
fast/canvas/canvas-large-fills.html
fast/canvas/text-globalAlpha.html
fast/canvas/canvas-draw-canvas-on-canvas-shadow.html
fast/canvas/canvas-strokePath-shadow.html
fast/canvas/canvas-strokeText-strokes-shadow.html

These tests don't fail under Win7.

Please check the attached archive for additional details. Also please notice the NPEs in *stderr files; there are no such NPEs under Windows.