[css-display] Make form controls and replaced elements behave like 'display: none'. Use a handwavy definition of “form control” until HTML has one we can refer to. w3c#1024 w3c#540

Author: fantasai

css-display/Overview.bs

@@ -482,9 +482,25 @@ Box Generation: the ''display/none'' and ''display/contents'' keywords</h3>
 			such as selector-matching and event handling,
 			are not affected.
 
-			This value has no effect on replaced elements and form controls;
-			it computes to ''inline'' exactly as if the UA style sheet had specified
-			''display: inline !important'' on such elements.
+			This value is treated as ''display: none'' on replaced elements,
+			form controls
+			(i.e. user interface elements whose element type
+			can accept and/or submit user data,
+			such as <code>&lt;input&gt;</code> and <code>&lt;button&gt;</code>),
+			and (obviously) empty elements.
+			The effect is exactly as if the UA style sheet had specified
+			''display: none !important'' on such elements,
+			except that the computed style is still ''contents''.
+
+			Note: Replaced elements and form controls are included in this special case
+			because their rendering requirements are often
+			outside the scope of the CSS formatting model,
+			and therefore removing only the element’s own generating box
+			is a more-or-less undefined operation.
+			As this behavior may be refined if use cases
+			(and more precise rendering models) develop,
+			authors should use ''display: none'' rather than ''display: contents''
+			on such elements for forward-compatibility.
 
 		<dt><dfn>none</dfn>
 		<dd>