Note effect of orientation metadata on naturalWidth and naturalHeight

Partially addresses whatwg#4495.

Author: heycam

source

@@ -3559,6 +3559,9 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      height</dfn></li>
      <li><dfn data-x-href="https://drafts.csswg.org/css-images/#intrinsic-width">intrinsic
      width</dfn></li>
+     <li>The <dfn
+     data-x-href="https://drafts.csswg.org/css-images-3/#the-image-orientation">'image-orientation'</dfn>
+     property</li>
     </ul>
 
     <p>The term <dfn data-x-href="https://drafts.csswg.org/css-images-4/#paint-source">paint
@@ -26855,6 +26858,14 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
   data-x="'px'">CSS pixels</span>, if the image has <span>intrinsic dimensions</span> and is <i
   data-x="img-available">available</i>, or else 0. <ref spec=CSS></p>
 
+  <div class="note">
+    <p>Since the <span>intrinsic dimensions</span> of an image take into account any
+    orientation specified in its metadata, <code data-x="dom-img-naturalWidth">naturalWidth</code>
+    and <code data-x="dom-img-naturalHeight">naturalHeight</code> reflect the dimensions after
+    applying any rotation <!--non-normative-->required to correctly orient the image, regardless of
+    the value of the <span>'image-orientation'</span> property.</p>
+  </div>
+
   <p>The IDL attribute <dfn data-x="dom-img-complete"><code>complete</code></dfn> must return true if
   any of the following conditions is true:</p>