[css-text] Correct replaced element linebreaking behavior to be like ideographics, with nbsp exception, per WG resolution https://lists.w3.org/Archives/Public/www-style/2015Mar/0187.html

Author: tabatkins

css-text/Overview.bs

@@ -905,12 +905,10 @@ Line Breaking Details</h3>
     <li>Out-of-flow elements do not introduce a <a>forced line break</a>
       or <a>soft wrap opportunity</a> in the flow.
     <li>The line breaking behavior of a replaced element or other atomic inline
-      is equivalent to that of the Object Replacement Character (U+FFFC)
-      and introduces a <a>soft wrap opportunity</a> both before and after itself.
-      For Web-compatibility, this rule take precedence over <code>WJ</code> and <code>GL</code> handling;
-      in terms of [[!UAX14]],
-      this shifts the <code>CB</code> rule (<a href="http://www.unicode.org/reports/tr14/#LB20"><code>LB20</code></a>)
-      immediately above the <code>WJ</code> and <code>GL</code> rules (<a href="http://www.unicode.org/reports/tr14/#LB11"><code>LB11</code></a>/<a href="http://www.unicode.org/reports/tr14/#LB12"><code>LB12</code></a>).
+      is equivalent to an ideographic character
+      (Unicode linebreaking class <code>ID</code> [[!UAX14]]),
+      and additionally, for Web-compatibility, introduces a <a>soft wrap opportunity</a>
+      between itself and any adjacent U+00A0 NO-BREAK SPACE character.
     <li>For <a>soft wrap opportunities</a> created by characters that disappear at the line break (e.g. U+0020 SPACE),
       properties on the element containing that character control the line breaking at that opportunity.
       For <a>soft wrap opportunities</a> defined by the boundary between two characters,