Reword the transitioning line and prose for 'flex'.

Author: tabatkins

css3-flexbox/Overview.html

@@ -1210,7 +1210,8 @@ <h2 id=flexibility><span class=secno>7. </span> Flexibility: the &lsquo;<a
     <tr>
      <th>Animatable:
 
-     <td>yes
+     <td>yes, as &lt;number> and &lt;length> or &lt;percentage>, but see
+      prose
   </table>
 
   <p>The &lsquo;<a href="#flex"><code class=property>flex</code></a>&rsquo;
@@ -1261,15 +1262,12 @@ <h2 id=flexibility><span class=secno>7. </span> Flexibility: the &lsquo;<a
   <p>The keyword &lsquo;<code class=property>none</code>&rsquo; computes to
    "0 0 auto".
 
-  <p>A &lsquo;<code class=css>&lt;flex></code>&rsquo; value is
-   transitionable, by transitioning the <a
-   href="#preferred-size"><i>preferred size</i></a>, <a
-   href="#positive-flexibility"><i>positive flexibility</i></a>, and <a
-   href="#negative-flexibility"><i>negative flexibility</i></a>
-   independently. &lsquo;<code class=css>&lt;flex></code>&rsquo; can also
-   transition to and from a &lt;length>, by treating the length as if it were
-   a flexible length with a positive and negative flexibility of zero and a
-   preferred size of the length.
+  <p>The &lsquo;<a href="#flex"><code class=property>flex</code></a>&rsquo;
+   property is transitionable if the <a href="#preferred-size"><i>preferred
+   size</i></a> is transitionable, by transitioning the <a
+   href="#positive-flexibility"><i>positive flexibility</i></a>, <a
+   href="#negative-flexibility"><i>negative flexibility</i></a>, and <a
+   href="#preferred-size"><i>preferred size</i></a> independently.
 
   <div class=example>
    <p>Flexibility allows elements to respond directly to the available space,

css3-flexbox/Overview.src.html

@@ -593,7 +593,7 @@ <h2 id='flexibility'>
 			<td>visual
 		<tr>
 			<th>Animatable:
-			<td>yes
+			<td>yes, as &lt;number> and &lt;length> or &lt;percentage>, but see prose
 	</table>
 
 	<p>The 'flex' property specifies the parameters of a <dfn title="flexible length|flexible lengths|flexible length's">flexible length</dfn>: the <dfn id="positive-flexibility" title="positive flexibility">positive</dfn> and <dfn>negative flexibility</dfn>, and the <dfn>preferred size</dfn>.  When the element containing 'flex' is a <i>flexbox item</i>, 'flex' is consulted <em>instead of</em> the <i>main size property</i> to determine the <i>main size</i> of the element.  If an element is not a <i>flexbox item</i>, 'flex' has no effect.</p>
@@ -605,8 +605,8 @@ <h2 id='flexibility'>
 	<p>If the <code>&lt;preferred-size></code> is ''0'', it <strong>must</strong> be specified with a unit (like ''0px'') to avoid ambiguity; unitless zero will either be interpreted as as one of the flexibilities, or is a syntax error.</p>
 
 	<p>The keyword 'none' computes to "0 0 auto". </p>
-	
-	<p>A ''&lt;flex>'' value is transitionable, by transitioning the <i>preferred size</i>, <i>positive flexibility</i>, and <i>negative flexibility</i> independently.  ''&lt;flex>'' can also transition to and from a &lt;length>, by treating the length as if it were a flexible length with a positive and negative flexibility of zero and a preferred size of the length.</p>
+
+	<p>The 'flex' property is transitionable if the <i>preferred size</i> is transitionable, by transitioning the <i>positive flexibility</i>, <i>negative flexibility</i>, and <i>preferred size</i> independently.</p>
 
 	<div class='example'>
 		<p>Flexibility allows elements to respond directly to the available space,