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

third_party/WebKit/LayoutTests/virtual/threaded/fast/idleToBlob/OffscreenCanvas-convertToBlob-2d-main.html

-<img id="png"/>
-<img id="jpeg-high"/>
-<img id="jpeg-low"/>
-<img id="webp-high"/>
-<img id="webp-low"/>
-<script type="text/javascript">
-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 offCanvas = new OffscreenCanvas(50, 50);
-var offctx = offCanvas.getContext('2d');
-offctx.fillStyle = "red";
-offctx.fillRect(0, 0, 25, 25);
-offctx.fillStyle = "green";
-offctx.fillRect(25, 0, 25, 25);
-offctx.fillStyle = "blue";
-offctx.fillRect(0, 25, 25, 25);
-offctx.fillStyle = "black";
-offctx.fillRect(25, 25, 25, 25);
-offctx.strokeStyle = "yellow";
-offctx.strokeRect(0, 0, 50, 50);
-
-offCanvas.convertToBlob()
-  .then(function(blob) { 
-    pngImage.src = URL.createObjectURL(blob);
-  });
-
-offCanvas.convertToBlob({type: "image/jpeg"})
-  .then(function(blob) {
-    jpegImageHigh.src = URL.createObjectURL(blob);
-  });
-
-offCanvas.convertToBlob({type: "image/jpeg", quality: 0.2})
-  .then(function(blob) {
-    jpegImageLow.src = URL.createObjectURL(blob);
-  });
-
-offCanvas.convertToBlob({type: "image/webp"})
-  .then(function(blob) { 
-    webpImageHigh.src = URL.createObjectURL(blob);
-  });
-
-offCanvas.convertToBlob({type: "image/webp", quality: 0.2})
-  .then(function(blob) {
-    webpImageLow.src = URL.createObjectURL(blob);
-  });
-
-</script>
-