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

third_party/WebKit/LayoutTests/imported/wpt/offscreen-canvas/path-objects/2d.path.stroke.overlap.worker.js

-// DO NOT EDIT! This test has been generated by tools/gentest.py.
-// OffscreenCanvas test in a worker:2d.path.stroke.overlap
-// Description:Stroked subpaths are combined before being drawn
-// Note:
-
-importScripts("/resources/testharness.js");
-importScripts("/common/canvas-tests.js");
-
-var t = async_test("Stroked subpaths are combined before being drawn");
-t.step(function() {
-
-var offscreenCanvas = new OffscreenCanvas(100, 50);
-var ctx = offscreenCanvas.getContext('2d');
-
-ctx.fillStyle = '#000';
-ctx.fillRect(0, 0, 100, 50);
-ctx.strokeStyle = 'rgba(0, 255, 0, 0.5)';
-ctx.lineWidth = 50;
-ctx.moveTo(0, 20);
-ctx.lineTo(100, 20);
-ctx.moveTo(0, 30);
-ctx.lineTo(100, 30);
-ctx.stroke();
-_assertPixelApprox(offscreenCanvas, 50,25, 0,127,0,255, "50,25", "0,127,0,255", 1);
-
-t.done();
-
-});
-done();