[css-images-3] Deprecate image-orientation and make it optional per <https://lists.w3.org/Archives/Public/www-style/2019Aug/0005.html>. Related to discussion in w3c#4164

Author: fantasai

css-images-3/Overview.bs

@@ -1495,8 +1495,6 @@ Image Processing {#image-processing}
 
 <h3 id="the-image-orientation" caniuse="css-image-orientation">Orienting an Image on the Page: the 'image-orientation' property </h3>
 
-	Issue: This property is likely going to be deprecated and its functionality moved to HTML.
-	At minimum, it will likely lose all but its initial value and ''image-orientation/from-image''.
 
 	If a picture is taken with a camera turned on its side,
 	or a document isn't positioned correctly within a scanner,
@@ -1520,6 +1518,17 @@ Image Processing {#image-processing}
 	Animation type: discrete
 	</pre>
 
+	<strong>This property is deprecated,
+	and is <em>optional</em> for implementations.</strong>
+
+	Note: This property previously used ''image-orientation/none'' as its initial value.
+	It is believed that using ''from-image'' as the initial value
+	will produce a generally better user experience,
+	and minimal breakage,
+	but future compat data as UAs attempt to make the change will confirm that.
+	If that is confirmed, then it is likely that this property will be removed from CSS
+	unless use cases other than “correct for incorrect orientation” are raised for its other values.
+
 	This property specifies an orthogonal rotation to be applied to an image before it is laid out.
 	It applies only to content images
 	(e.g. replaced elements and generated content),
@@ -1548,19 +1557,7 @@ Image Processing {#image-processing}
 			If necessary, this angle is then rounded and normalized as described above for an <<angle>> value.
 			If there is no orientation specified in its metadata,
 			this value computes to ''image-orientation/none''.
-	</dl>
 
-	Note: This property previously used ''image-orientation/none'' as its initial value.
-	It is believed that using ''from-image'' as the initial value
-	will produce a generally better user experience,
-	and minimal breakage,
-	but future compat data as UAs attempt to make the change will confirm that.
-
-	Values other than ''image-orientation/none'' and ''from-image'' are
-	<em>optional</em> to implement and <em>deprecated</em> in CSS.
-	They have the following meanings:
-
-	<dl dfn-type=value dfn-for=image-orientation>
 		<dt><dfn><<angle>></dfn>
 		<dd>
 			Positive values cause the image to be rotated to the right
@@ -1583,6 +1580,11 @@ Image Processing {#image-processing}
 			Note: This value is only necessary to represent all 8 possible EXIF orientations that <a value for=image-orientation>from-image</a> can produce.
 	</dl>
 
+<!--
+	Values other than ''image-orientation/none'' and ''from-image'' are
+	<em>optional</em> to implement and <em>deprecated</em> in CSS.
+-->
+
 	The 'image-orientation' property must be applied before any other transformations,
 	such as using CSS Transforms.