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

third_party/WebKit/LayoutTests/imported/wpt/offscreen-canvas/fill-and-stroke-styles/2d.gradient.interpolate.overlap2.worker.js

-// DO NOT EDIT! This test has been generated by tools/gentest.py.
-// OffscreenCanvas test in a worker:2d.gradient.interpolate.overlap2
-// Description:
-// Note:
-
-importScripts("/resources/testharness.js");
-importScripts("/common/canvas-tests.js");
-
-var t = async_test("");
-t.step(function() {
-
-var offscreenCanvas = new OffscreenCanvas(100, 50);
-var ctx = offscreenCanvas.getContext('2d');
-
-var g = ctx.createLinearGradient(0, 0, 100, 0);
-var ps = [ 0, 1/10, 1/4, 1/3, 1/2, 3/4, 1 ];
-for (var p = 0; p < ps.length; ++p)
-{
-        g.addColorStop(ps[p], '#0f0');
-        for (var i = 0; i < 15; ++i)
-                g.addColorStop(ps[p], '#f00');
-        g.addColorStop(ps[p], '#0f0');
-}
-ctx.fillStyle = g;
-ctx.fillRect(0, 0, 100, 50);
-_assertPixel(offscreenCanvas, 1,25, 0,255,0,255, "1,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 30,25, 0,255,0,255, "30,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 40,25, 0,255,0,255, "40,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 60,25, 0,255,0,255, "60,25", "0,255,0,255");
-_assertPixel(offscreenCanvas, 80,25, 0,255,0,255, "80,25", "0,255,0,255");
-
-t.done();
-
-});
-done();