Improve the LayoutTest related with Config conversions for Canvas2D

LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js

Index: LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js
diff --git a/LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js b/LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js
index f28b9dbee3b129cbbd6d65c33a7088b97e3c90f8..39d6ada7dd0aa7df7f89c8772128645639dc58d7 100644
--- a/LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js
+++ b/LayoutTests/fast/canvas/script-tests/canvas-fillPath-shadow.js
@@ -73,7 +73,7 @@ shouldBe('data[2]', '0');
 imageData = ctx.getImageData(380, 30, 1, 1);
 data = imageData.data;
 shouldBe('data[0]', '255');
-shouldBe('data[1]', '20');
+shouldBeCloseTo('data[1]', 20, 3);
 shouldBe('data[2]', '0');
 
 imageData = ctx.getImageData(400, 40, 1, 1);