Merge pull request w3c#4309 from jihyerish/update-the-search-origin

[css-nav-1] Update the search origin after scrolling

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1089,17 +1089,18 @@ run the following steps:
     then return it.
 3. Otherwise, return <var>searchOrigin</var>.
 
-If the status of <var>old focus target</var> changed not by the spatial navigation,
+If the status of <var>old focus target</var> changed not by moving the focus,
 <dfn lt="update the search origin | updating the search origin">update the <a>search origin</a></dfn> as following:
-1. If <var>old focus target</var> becomes
+1. If <var>old focus target</var> is
     <a>actually disabled</a> or
     <a>expressly inert</a> or
     not <a>being rendered</a>,
     then let <var>searchOrigin</var> be the [=boundary box=] of <var>old focus target</var>.
 2. If <var>old focus target</var> is <a>removed</a>,
     then let <var>searchOrigin</var> be the [=boundary box=] of <var>old focus target</var> with the position of <var>old focus target</var> when it existed.
-3. Otherwise,
-    let <var>searchOrigin</var> be the viewport of <var>old focus target</var>'s <a>spatial navigation container</a>.
+3. If <var>old focus target</var> is completely off-screen,
+    then let <var>searchOrigin</var> be the viewport of <var>old focus target</var>'s <a>spatial navigation container</a>.
+
 </div>
 
 <div algorithm="to find focusable areas">