Removal all idle-task implementations in toBlob

third_party/WebKit/LayoutTests/fast/canvas/toBlob/canvas-toBlob-defaultpng.html

-<script src = "../../../resources/js-test.js"></script>
-<script type = 'text/javascript'>
-jsTestIsAsync = true;
-description("Test that verifies whether the image data survives the toBlob process after async image encoding");
-
-if (window.testRunner) {
-    testRunner.waitUntilDone();
-}
-
-var canvas = document.createElement("canvas");
-var ctx = canvas.getContext("2d");
-ctx.fillStyle = "#FF0000";
-ctx.fillRect(0, 0, 150, 75);
-var canvas2 = document.createElement("canvas");
-var ctx2 = canvas2.getContext("2d");
-
-var newImg = new Image();
-newImg.onload = function() {
-    // 300x150 is the default size of the canvas, which is the source of the newImg.
-    ctx2.drawImage(newImg, 0, 0, 300, 150);
-
-    var imageData1 = ctx.getImageData(0, 0, 150, 75).data;
-    var imageData2 = ctx2.getImageData(0, 0, 150, 75).data;
-    var imageMatched = true;
-    for (var i = 1; i < imageData1.length; i++)
-    {
-        if (imageData1[i]!=imageData2[i])
-        {
-            imageMatched = false;
-            break;
-        }
-    }
-    if (imageMatched)
-        testPassed("image data survives through the toBlob and PNG Image encoder");
-    else 
-        testFailed("image data does not survive through the toBlob and PNG Image encoder");
-
-    finishJSTest();
-}
-
-canvas.toBlob(function(blob) {
-    url = URL.createObjectURL(blob);
-    newImg.src = url;
-});
-
-</script>