Make ImageBitmap Transferable

third_party/WebKit/LayoutTests/fast/canvas/resources/canvas-ImageBitmap-transferable.js

+self.onmessage = function(e) {
+  // Worker does two things:
+  // 1. call createImageBitmap() from the ImageBitmap that is transfered
+  // from the main thread, which verifies that createImageBitmap(ImageBitmap)
+  // works on the worker thread.
+  // 2. send the created ImageBitmap back to the main thread, the
+  // main thread exam the property of this ImageBitmap to make sure
+  // the transfer between main and worker thread didn't lose data
+  createImageBitmap(e.data.data).then(imageBitmap => {
+    postMessage({data: imageBitmap}, [imageBitmap]);
+  });
+};