[css-text-3] Tentative commits for #855.

Author: fantasai

css-text-3/Overview.bs

@@ -428,7 +428,8 @@ Languages and Typesetting</h4>
       in order to minimize inline-axis overflow.
     <dt><dfn>pre</dfn></dt>
     <dd>This value prevents user agents from collapsing sequences of <a>white space</a>.
-      <a>Segment breaks</a> such as line feeds and carriage returns are preserved as <a>forced line breaks</a>.
+      <a>Segment breaks</a> such as line feeds
+      are preserved as <a>forced line breaks</a>.
       Lines only break at <a>forced line breaks</a>;
       content that does not fit within the block container overflows it.
     <dt><dfn>nowrap</dfn>
@@ -524,8 +525,8 @@ Languages and Typesetting</h4>
     separated by a particular newline sequence (such as a line feed or
     CRLF pair), or delimited by some other mechanism, such as the SGML
     <code>RECORD-START</code> and <code>RECORD-END</code> tokens.
-    For CSS processing, each document language&ndash;defined segment break,
-    CRLF sequence (U+000D U+000A), carriage return (U+000D), and line feed (U+000A)
+    For CSS processing, each document language&ndash;defined segment break
+    and each line feed (U+000A)
     in the text is treated as a <dfn export>segment break</dfn>,
     which is then interpreted for rendering as specified by the 'white-space' property.
 
@@ -546,6 +547,9 @@ Languages and Typesetting</h4>
     <a href="https://www.w3.org/TR/CSS21/visuren.html#anonymous">9.2.2.1</a></p>
 
   <p>
+    Form feeds (U+000C) and carriage returns (U+000D)
+    (that are not <a>segment breaks</a>)
+    are <span class="issue">not rendered | rendered as a zero-width space</span>.
     Control characters (<a>Unicode category</a> <code>Cc</code>)
     other than tab (U+0009), line feed (U+000A), form feed (U+000C), and carriage return (U+000D)
     must be rendered as a visible glyph