Document the Web Animation interfaces with spec links and TODOs

Source/core/animation/Animation.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
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  * modification, are permitted provided that the following conditions are
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  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 10 matching lines @@
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  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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-// http://dev.w3.org/fxtf/web-animations/#idl-def-Animation
+// http://www.w3.org/TR/web-animations/#the-animation-interface
+
+// TODO(dstockwell): This interface has been renamed to KeyframeEffect in the
+// latest spec:
+// https://w3c.github.io/web-animations/#the-keyframeeffect-interfaces
 
 [
     // FIXME: the third argument should be "optional (unrestricted double or AnimationTimingProperties) timing".
     Constructor(Element? target, sequence<Dictionary> keyframes, optional unrestricted double timing),
     Constructor(Element? target, sequence<Dictionary> keyframes, AnimationTimingProperties timing),
     RaisesException=Constructor,
     RuntimeEnabled=WebAnimationsAPI,
     TypeChecking=Interface,
 ] interface Animation : AnimationNode {
 };