Adding nullability support to ImageBitmapRenderingContext.transferImageBitmap

third_party/WebKit/Source/modules/imagebitmap/ImageBitmapRenderingContext.idl

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
     RuntimeEnabled=ExperimentalCanvasFeatures,
     SetWrapperReferenceFrom=canvas,
 ] interface ImageBitmapRenderingContext {
     // back-reference to the canvas
     readonly attribute HTMLCanvasElement canvas;
 
-    void transferFromImageBitmap(ImageBitmap bitmap);
+    void transferFromImageBitmap(ImageBitmap? bitmap);
 };