Fixing dart:html links _not_ found in docs.json

tools/dom/src/CanvasImageSource.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of html;
 
 /**
  * An object that can be drawn to a 2D canvas rendering context.
  *
  * The image drawn to the canvas depends on the type of this object:
@@ skipping 15 matching lines @@
  *
  * ## See also
  *
  * * [CanvasRenderingContext2D.drawImage]
  * * [CanvasRenderingContext2D.drawImageToRect]
  * * [CanvasRenderingContext2D.drawImageScaled]
  * * [CanvasRenderingContext2D.drawImageScaledFromSource]
  *
  * ## Other resources
  *
- * * [Image sources for 2D rendering contexts]
- * (http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#image-sources-for-2d-rendering-contexts)
- * from WHATWG.
- * * [Drawing images]
- * (http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-drawimage)
- * from WHATWG.
+ * * [Image sources for 2D rendering
+ *   contexts](https://html.spec.whatwg.org/multipage/scripting.html#image-sources-for-2d-rendering-contexts)
+ *   from WHATWG.
+ * * [Drawing images](https://html.spec.whatwg.org/multipage/scripting.html#dom-context-2d-drawimage)
+ *   from WHATWG.
  */
 abstract class CanvasImageSource {}