The type argument for HTMLCanvasElement toDataURL() api should not be nullable

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 b6d326c40df78aff6e2585d905f6867b69643a5c..57ead8bcb8e8971c58665b2d167f008b310e5aee 100644
--- a/Source/core/html/HTMLCanvasElement.idl
+++ b/Source/core/html/HTMLCanvasElement.idl
@@ -49,6 +49,6 @@ interface HTMLCanvasElement : HTMLElement {
 
     // Note: The arguments argument is variadic in the spec, but not here as
     // only one extra argument is actually used.
-    // FIXME: type should not be nullable or have a default value.
-    [RaisesException] DOMString toDataURL(optional DOMString? type = null, optional any arguments);
+    // FIXME: type should not have a default value.
+    [RaisesException] DOMString toDataURL(optional DOMString type = null, optional any arguments);
 };