Several canvas tests fail with Ubuntu 16.04:
canvas/philip/tests/2d.drawImage.self.1.html
canvas/philip/tests/2d.line.cap.butt.html
canvas/philip/tests/2d.line.cap.square.html
canvas/philip/tests/2d.line.join.round.html
canvas/philip/tests/2d.line.width.basic.html
canvas/philip/tests/2d.line.width.transformed.html
fast/canvas/canvas-getImageData.html
fast/canvas/canvas-lineWidth.html

The following tests fail intermittently:
canvas/philip/tests/2d.line.cap.round.html
canvas/philip/tests/2d.shadow.stroke.basic.html
canvas/philip/tests/2d.shadow.stroke.cap.2.html
canvas/philip/tests/2d.shadow.stroke.join.2.html
canvas/philip/tests/2d.transformation.setTransform.skewed.html
canvas/philip/tests/2d.transformation.transform.skewed.html
fast/canvas/canvas-strokePath-cap-join.html