Add offscreen-canvas to the list of wpt directories to skip.

third_party/WebKit/LayoutTests/imported/wpt/offscreen-canvas/line-styles/2d.line.width.scaledefault.worker.js

-// DO NOT EDIT! This test has been generated by tools/gentest.py.
-// OffscreenCanvas test in a worker:2d.line.width.scaledefault
-// Description:Default lineWidth strokes are affected by scale transformations
-// Note:
-
-importScripts("/resources/testharness.js");
-importScripts("/common/canvas-tests.js");
-
-var t = async_test("Default lineWidth strokes are affected by scale transformations");
-t.step(function() {
-
-var offscreenCanvas = new OffscreenCanvas(100, 50);
-var ctx = offscreenCanvas.getContext('2d');
-
-ctx.fillStyle = '#f00';
-ctx.fillRect(0, 0, 100, 50);
-ctx.scale(50, 50);
-ctx.strokeStyle = '#0f0';
-ctx.moveTo(0, 0.5);
-ctx.lineTo(2, 0.5);
-ctx.stroke();
-_assertPixel(offscreenCanvas, 25,25, 0,255,0,255, "25,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 50,25, 0,255,0,255, "50,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 75,25, 0,255,0,255, "75,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 50,5, 0,255,0,255, "50,5", "0,255,0,255");
-_assertPixel(offscreenCanvas, 50,45, 0,255,0,255, "50,45", "0,255,0,255");
-
-t.done();
-
-});
-done();