Removing --disable/enable-threaded-compositing cmdline switches.

third_party/WebKit/LayoutTests/virtual/threaded/fast/idleToBlob/OffscreenCanvas-convertToBlob-webgl-worker-expected.html

-<img id="png"/>
-<img id="jpeg-high"/>
-<img id="jpeg-low"/>
-<img id="webp-high"/>
-<img id="webp-low"/>
-<script>
-if (window.testRunner) {
-  testRunner.waitUntilDone();
-}
-
-var pngImage = document.getElementById('png');
-var jpegImageHigh = document.getElementById('jpeg-high');
-var jpegImageLow = document.getElementById('jpeg-low');
-var webpImageHigh = document.getElementById('webp-high');
-var webpImageLow = document.getElementById('webp-low');
-var numTestCount = 5;
-function imageLoaded() {
-  numTestCount--;
-  if (numTestCount == 0 && window.testRunner) {
-    window.testRunner.notifyDone();
-  }
-}
-pngImage.addEventListener('load', imageLoaded);
-jpegImageHigh.addEventListener('load', imageLoaded);
-jpegImageLow.addEventListener('load', imageLoaded);
-webpImageHigh.addEventListener('load', imageLoaded);
-webpImageLow.addEventListener('load', imageLoaded);
-
-var canvas = document.createElement("canvas");
-canvas.width = 50;
-canvas.height = 50;
-var gl = canvas.getContext('webgl');
-gl.clearColor(0, 1, 0, 1);
-gl.clear(gl.COLOR_BUFFER_BIT);
-
-canvas.toBlob(function(blob) {
-  pngImage.src = URL.createObjectURL(blob);
-});
-
-canvas.toBlob(function(blob) {
-  jpegImageHigh.src = URL.createObjectURL(blob);
-}, "image/jpeg", 1.0);
-
-canvas.toBlob(function(blob) {
-    jpegImageLow.src = URL.createObjectURL(blob);
-}, "image/jpeg", 0.2)
-
-canvas.toBlob(function(blob) {
-    webpImageHigh.src = URL.createObjectURL(blob);
-}, "image/webp", 1.0);
-
-canvas.toBlob(function(blob) {
-    webpImageLow.src = URL.createObjectURL(blob);
-}, "image/webp", 0.2);
-
-</script>
-