[css-text] Add rule for web-compatible atomic inline breaking. <http://dev.w3.org/csswg/css-text-3/issues-lc-2013#issue-4>

Author: fantasai

css-text/Overview.bs

@@ -747,7 +747,12 @@ Line Breaking Details</h3>
     <li>Out-of-flow elements do not introduce a <i>forced line break</i>
       or <i>soft wrap opportunity</i> 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).
+      is equivalent to that of the Object Replacement Character (U+FFFC)
+      and introduces a <i>soft wrap opportunity</i> 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>).
     <li>For <i>soft wrap opportunities</i> 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 <i>soft wrap opportunities</i> defined by the boundary between two characters,