Gloss the CSS term "line box"

PR: #768

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@@ -3342,6 +3342,7 @@ a.setAttribute('href', 'http://example.com/'); // change the content attribute d
 
     <ul class="brief">
       <li><dfn data-noexport="" data-x-href="https://drafts.csswg.org/css2/visuren.html#viewport">viewport</dfn></li>
+      <li><dfn data-noexport="" data-x-href="https://drafts.csswg.org/css2/visuren.html#line-box">line box</dfn></li>
       <li><dfn data-noexport="" data-x-href="https://drafts.csswg.org/css2/conform.html#replaced-element">replaced element</dfn></li>
       <li><dfn data-noexport="" data-x-href="https://drafts.csswg.org/css2/conform.html#intrinsic">intrinsic dimensions</dfn></li>
     </ul>
@@ -61623,17 +61624,17 @@ transform. ack Shaun Morris. -->
 
    </li>
 
-   <li><p>Form a hypothetical infinitely-wide CSS line box containing a single inline box containing
-   the text <var>text</var>, with all the properties at their initial values except the
-   'font' property of the inline box set to <var>font</var>, the 'direction' property of
+   <li><p>Form a hypothetical infinitely-wide CSS <span>line box</span> containing a single
+   inline box containing the text <var>text</var>, with all the properties at their initial values
+   except the 'font' property of the inline box set to <var>font</var>, the 'direction' property of
    the inline box set to <var>direction</var>, and the 'white-space' property set to 'pre'.
    <ref spec=CSS></p></li>
 
    <!-- if you insert a step here, make sure to adjust the next step's final words -->
 
    <li><p>If <var>maxWidth</var> was provided and the hypothetical width of the inline box
-   in the hypothetical line box is greater than <var>maxWidth</var> CSS pixels, then change
-   <var>font</var> to have a more condensed font (if one is available or if a reasonably
+   in the hypothetical <span>line box</span> is greater than <var>maxWidth</var> CSS pixels, then
+   change <var>font</var> to have a more condensed font (if one is available or if a reasonably
    readable one can be synthesized by applying a horizontal scale factor to the font) or a smaller
    font, and return to the previous step.</p></li>
 
@@ -63396,8 +63397,8 @@ HAVE REJIGGED HOW TEXT WORKS IN v5 (e.g. remember security)
    <!- - if you insert a step here, make sure to adjust the next step's final words - ->
 
    <li><p>If the <var>maxHeight</var> argument was specified and the hypothetical height of
-   the <em class="&#x0058;&#x0058;&#x0058;">box</em> in the hypothetical line box is greater than
-   <var>maxHeight</var> CSS pixels, then change <var>font</var> to have a more
+   the <em class="&#x0058;&#x0058;&#x0058;">box</em> in the hypothetical <span>line box</span> is
+   greater than <var>maxHeight</var> CSS pixels, then change <var>font</var> to have a more
    condensed font (if one is available or if a reasonably readable one can be synthesized by
    applying an appropriate scale factor to the font) or a smaller font, and return to the previous
    step.</p></li>
@@ -63586,39 +63587,39 @@ v6DVT (also check for '- -' bits in the part above) -->
 
    <dd><p>The distance from the horizontal line indicated by the <code
    data-x="dom-context-2d-textBaseline">textBaseline</code> attribute to the highest top of the em
-   squares in the line box, in CSS pixels; positive numbers indicating that the given baseline is
-   below the top of that em square (so this value will usually be positive). Zero if the given
-   baseline is the top of that em square; half the font size if the given baseline is the middle of
-   that em square.</p></dd>
+   squares in the <span>line box</span>, in CSS pixels; positive numbers indicating that the given
+   baseline is below the top of that em square (so this value will usually be positive). Zero if the
+   given baseline is the top of that em square; half the font size if the given baseline is the
+   middle of that em square.</p></dd>
 
    <dt><dfn><code data-x="dom-textmetrics-emHeightDescent">emHeightDescent</code></dfn> attribute</dt>
 
    <dd><p>The distance from the horizontal line indicated by the <code
    data-x="dom-context-2d-textBaseline">textBaseline</code> attribute to the lowest bottom of the em
-   squares in the line box, in CSS pixels; positive numbers indicating that the given baseline is
-   below the bottom of that em square (so this value will usually be negative). (Zero if the given
-   baseline is the top of that em square.)</p></dd>
+   squares in the <span>line box</span>, in CSS pixels; positive numbers indicating that the given
+   baseline is below the bottom of that em square (so this value will usually be negative). (Zero if
+   the given baseline is the top of that em square.)</p></dd>
 
    <dt><dfn><code data-x="dom-textmetrics-hangingBaseline">hangingBaseline</code></dfn> attribute</dt>
 
    <dd><p>The distance from the horizontal line indicated by the <code
    data-x="dom-context-2d-textBaseline">textBaseline</code> attribute to the hanging baseline of the
-   line box, in CSS pixels; positive numbers indicating that the given baseline is below the hanging
-   baseline. (Zero if the given baseline is the hanging baseline.)</p></dd>
+   <span>line box</span>, in CSS pixels; positive numbers indicating that the given baseline is
+   below the hanging baseline. (Zero if the given baseline is the hanging baseline.)</p></dd>
 
    <dt><dfn><code data-x="dom-textmetrics-alphabeticBaseline">alphabeticBaseline</code></dfn> attribute</dt>
 
    <dd><p>The distance from the horizontal line indicated by the <code
    data-x="dom-context-2d-textBaseline">textBaseline</code> attribute to the alphabetic baseline of
-   the line box, in CSS pixels; positive numbers indicating that the given baseline is below the
-   alphabetic baseline. (Zero if the given baseline is the alphabetic baseline.)</p></dd>
+   the <span>line box</span>, in CSS pixels; positive numbers indicating that the given baseline is
+   below the alphabetic baseline. (Zero if the given baseline is the alphabetic baseline.)</p></dd>
 
    <dt><dfn><code data-x="dom-textmetrics-ideographicBaseline">ideographicBaseline</code></dfn> attribute</dt>
 
    <dd><p>The distance from the horizontal line indicated by the <code
    data-x="dom-context-2d-textBaseline">textBaseline</code> attribute to the ideographic baseline of
-   the line box, in CSS pixels; positive numbers indicating that the given baseline is below the
-   ideographic baseline. (Zero if the given baseline is the ideographic baseline.)</p></dd>
+   the <span>line box</span>, in CSS pixels; positive numbers indicating that the given baseline is
+   below the ideographic baseline. (Zero if the given baseline is the ideographic baseline.)</p></dd>
 
   </dl>