[css-inline-3] Inlinify the contents of an initial letter that is a non-atomic inline.

Author: fantasai

css-inline-3/Overview.bs

@@ -603,6 +603,26 @@ Properties</h4>
 	Additionally, all of the <a>sizing properties</a>
 	and 'box-sizing' also apply to <a>initial letters</a>.
 
+<h4 id="initial-letter-inlinification">
+Inlinification</h4>
+
+	The UA must ensure
+	that all the contents of an <a>initial letter</a>
+	that is not an <a>atomic inline</a>
+	are <a>inline-level</a>
+	by:
+
+	<ul>
+		<li><a>Inlinifying</a> its children. (See [[css-display-3#transformations]].)
+		<li><a>Suppressing line breaks</a>
+		by converting all forced line breaks
+		as defined for <a>collapsible</a> segment breaks in [[css-text-3#line-break-transform]].
+	</ul>
+
+	Note: This is the same set of transformations
+	applied to the content of <a>ruby annotations</a>
+	in [[css-ruby-1]].
+
 <h4 id="initial-letter-model">
 Layout Model</h4>