[css-nav-1] Drop inside option from spatialNavigationSearch API

Drop `inside` option from `spatialNavigationSearch` because it's risky

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -462,7 +462,6 @@ dictionary FocusableAreasOption {
 dictionary SpatialNavigationSearchOptions {
     sequence<Node>? candidates;
     Node? container;
-    boolean inside = false;
 };
 
 partial interface Element {
@@ -540,13 +539,7 @@ the User Agent must run the steps described below:
         if it is not <code>null</code>, the element's nearest <a>spatial navigation container</a> ancestor otherwise.
     3. Let <var>areas</var> be the value of {{SpatialNavigationSearchOptions/candidates}} attribute of <var>options</var>
         if it is not <code>null</code>, result of <a>finding focusable areas</a> within <var>container</var> otherwise.
-    4. Let <var>insideFirst</var> be the value of {{SpatialNavigationSearchOptions/inside}} attribute of <var>options</var>
-        if it is not <code>null</code>, <code>false</code> otherwise.
-    5. If <var>insideFirst</var> is <code>true</code>,
-        then let <var>bestCandidate</var> be the result of <a>selecting the best candidate</a> among <var>areas</var> within the element with <var>direction</var>.
-        * If <var>bestCandidate</var> is not <code>null</code>, return <var>bestCandidate</var>. 
-        * Else, fall back to the next step.
-    6. Return the result of <a>selecting the best candidate</a> among <var>areas</var> in <var>direction</var> from the element.
+    4. Return the result of <a>selecting the best candidate</a> among <var>areas</var> within <var>container</var> in <var>direction</var> from the element.
 
 Note: When neither a container nor a list of candidates is provided,
 this only searches through the visible focusable areas of the nearest
@@ -622,36 +615,6 @@ and the result will be <code>null</code>.</em>
 </div>
 </div>
 
-<div class=example id=searchInside>
-    This example shows different results of {{Element/spatialNavigationSearch()}}
-    depending on the value of {{SpatialNavigationSearchOptions/inside}} attribute.
-
-    When the page has the code snippet as below,
-
-    <pre><code highlight=markup>
-    &lt;body>
-        &lt;div id="container" style="width:300px; height:200px; overflow-y: scroll;">
-            &lt;button id="button1" style = "width:50px; height:50px;">&lt;/button>
-        &lt;/div>
-        &lt;button id="button2" style = "width:50px; height:50px;">&lt;/button>
-    &lt;/body>
-    </code></pre>
-
-    <pre><code highlight=javascript>
-        const container = document.getElementById('container');
-
-        const innerBtn = container.spatialNavigationSearch('down', {inside: true});
-        const outerBtn = container.spatialNavigationSearch('down');
-    </code></pre>
-
-    <code>innerBtn</code> is assigned to the element whose {{Element/id}} matches with <code>button1</code>
-    because the {{SpatialNavigationSearchOptions/inside}} attribute is <code>true</code>.
-    But if the author doesn't specify {{SpatialNavigationSearchOptions/inside}} attribute,
-    <code>false</code> is given to it by default. 
-    Therefore <code>outerBtn</code> is assigned to the element with {{Element/id}} <code>button2</code>
-    which is outside of <code>container</code>.
-</div>
-
 <div class=api>
 <h2 id="events-navigationevent">
 Navigation Events</h2>