Separator in AbsListView should not be clickable

In ListAdapter, isEnabled (int position) returns true if the
item at the specified position is not a separator. (A
separator is a non-selectable, non-clickable item). So we should
not set it to clickable in accessibility node info when the item
is disabled.

Bug: 140017328
Test: After the fix, talkback focus will skip the separator in
linear navigation.

Change-Id: Id0a76a2f93b8af730dab1a808dc24a0ae24bcee0

core/java/android/widget/AbsListView.java

@@ -2569,7 +2569,8 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
 
         if (isItemClickable(view)) {
             addAccessibilityActionIfEnabled(info, isItemEnabled, AccessibilityAction.ACTION_CLICK);
-            info.setClickable(true);
+            // A disabled item is a separator which should not be clickable.
+            info.setClickable(isItemEnabled);
         }
 
         if (isLongClickable()) {