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

third_party/WebKit/LayoutTests/imported/wpt/offscreen-canvas/pixel-manipulation/2d.imageData.get.source.negative.worker.js

-// DO NOT EDIT! This test has been generated by tools/gentest.py.
-// OffscreenCanvas test in a worker:2d.imageData.get.source.negative
-// Description:getImageData() works with negative width and height, and returns top-to-bottom left-to-right
-// Note:
-
-importScripts("/resources/testharness.js");
-importScripts("/common/canvas-tests.js");
-
-var t = async_test("getImageData() works with negative width and height, and returns top-to-bottom left-to-right");
-t.step(function() {
-
-var offscreenCanvas = new OffscreenCanvas(100, 50);
-var ctx = offscreenCanvas.getContext('2d');
-
-ctx.fillStyle = '#000';
-ctx.fillRect(0, 0, 100, 50);
-ctx.fillStyle = '#fff';
-ctx.fillRect(20, 10, 60, 10);
-var imgdata1 = ctx.getImageData(85, 25, -10, -10);
-_assertSame(imgdata1.data[0], 255, "imgdata1.data[\""+(0)+"\"]", "255");
-_assertSame(imgdata1.data[1], 255, "imgdata1.data[\""+(1)+"\"]", "255");
-_assertSame(imgdata1.data[2], 255, "imgdata1.data[\""+(2)+"\"]", "255");
-_assertSame(imgdata1.data[3], 255, "imgdata1.data[\""+(3)+"\"]", "255");
-_assertSame(imgdata1.data[imgdata1.data.length-4+0], 0, "imgdata1.data[imgdata1.data.length-4+0]", "0");
-_assertSame(imgdata1.data[imgdata1.data.length-4+1], 0, "imgdata1.data[imgdata1.data.length-4+1]", "0");
-_assertSame(imgdata1.data[imgdata1.data.length-4+2], 0, "imgdata1.data[imgdata1.data.length-4+2]", "0");
-_assertSame(imgdata1.data[imgdata1.data.length-4+3], 255, "imgdata1.data[imgdata1.data.length-4+3]", "255");
-var imgdata2 = ctx.getImageData(0, 0, -1, -1);
-_assertSame(imgdata2.data[0], 0, "imgdata2.data[\""+(0)+"\"]", "0");
-_assertSame(imgdata2.data[1], 0, "imgdata2.data[\""+(1)+"\"]", "0");
-_assertSame(imgdata2.data[2], 0, "imgdata2.data[\""+(2)+"\"]", "0");
-_assertSame(imgdata2.data[3], 0, "imgdata2.data[\""+(3)+"\"]", "0");
-
-t.done();
-
-});
-done();