[HTMLCanvasElement.toBlob] Default callback version without scheduler

Source/core/html/HTMLCanvasElement.idl

Index: Source/core/html/HTMLCanvasElement.idl
diff --git a/Source/core/html/HTMLCanvasElement.idl b/Source/core/html/HTMLCanvasElement.idl
index 57ead8bcb8e8971c58665b2d167f008b310e5aee..4e7c0cf150b8e482cef42fdc4dee1e51ec4a137f 100644
--- a/Source/core/html/HTMLCanvasElement.idl
+++ b/Source/core/html/HTMLCanvasElement.idl
@@ -26,7 +26,8 @@
 
 // https://html.spec.whatwg.org/#the-canvas-element
 
-interface HTMLCanvasElement : HTMLElement {
+interface HTMLCanvasElement : HTMLElement
+{
     // FIXME: width and height should be unsigned long.
     attribute long width;
     attribute long height;
@@ -51,4 +52,6 @@ interface HTMLCanvasElement : HTMLElement {
     // only one extra argument is actually used.
     // FIXME: type should not have a default value.
     [RaisesException] DOMString toDataURL(optional DOMString type = null, optional any arguments);
+
+    [RaisesException, RuntimeEnabled=ExperimentalCanvasFeatures] void toBlob(FileCallback? _callback, optional DOMString type = null, optional any arguments);
 };