Add a regression test for focus behavior with slots that are assigned to a slot

third_party/WebKit/LayoutTests/shadow-dom/slot-assigned-slot.html

Index: third_party/WebKit/LayoutTests/shadow-dom/slot-assigned-slot.html
diff --git a/third_party/WebKit/LayoutTests/shadow-dom/slot-with-tabindex.html b/third_party/WebKit/LayoutTests/shadow-dom/slot-assigned-slot.html
similarity index 76%
copy from third_party/WebKit/LayoutTests/shadow-dom/slot-with-tabindex.html
copy to third_party/WebKit/LayoutTests/shadow-dom/slot-assigned-slot.html
index 483a54c60cbf9deef67294d05b0e515f072ca6db..66971e89f519cbc112ac3b49490adfe5f26f182f 100644
--- a/third_party/WebKit/LayoutTests/shadow-dom/slot-with-tabindex.html
+++ b/third_party/WebKit/LayoutTests/shadow-dom/slot-assigned-slot.html
@@ -7,11 +7,12 @@
 <p>
   document tree: [i0 -> [x-foo]]<br>
   x-foo's shadow tree: [j1 -> [s1] -> [s2] -> j2 ->[x-bar]]<br>
-  x-bar's shadow tree: [[s3] -> k1]<br>
+  x-bar's shadow tree: [k1 -> [s3]]<br>
   slot #s1: [i1 -> i2]<br>
   slot #s2: [i3]<br>
-  slot #s3: [l1 -> l2]<br><br>
-  <b>v1 ideal nav forward:  [i0 -> j1 -> i1 -> i2 -> i3 -> j2 -> x-bar -> l1 -> l2 -> k1]</b><br>
+  slot #s3: [[s4]]<br>
+  slot #s4: [i4 -> i5]<br><br>
+  <b>v1 ideal nav forward:  [i0 -> j1 -> i1 -> i2 -> i3 -> j2 -> x-bar -> k1 -> i4 -> i5]</b><br>
 </p>
 
 <input id="i0" tabindex=0 value="i0">
@@ -19,13 +20,14 @@
   <input id="i2" slot="s1" tabindex=2 value="i2">
   <input id="i1" slot="s1" tabindex=1 value="i1">
   <input id="i3" slot="s2" tabindex=3 value="i3">
+  <input id="i4" slot="s4" tabindex=4 value="i4">
+  <input id="i5" slot="s4" tabindex=5 value="i5">
   <template data-mode="open">
     <div id="x-bar" tabindex=5>
-      <input id="l2" slot="s3" tabindex=2 value="l2">
-      <input id="l1" slot="s3" tabindex=1 value="l1">
+      <slot id="s4" name="s4" slot="s3"></slot>
       <template data-mode="open">
-        <slot id="s3" name="s3" tabindex=1></slot>
-        <input id="k1" tabindex=2 value="k1">
+        <slot id="s3" name="s3" tabindex=2></slot>
+        <input id="k1" tabindex=1 value="k1">
       </template>
     </div>
     <input id="j1" tabindex=1 value="j1">
@@ -49,9 +51,9 @@ test(function() {
     'i3',
     'x-foo/j2',
     'x-foo/x-bar',
-    'x-foo/l1',
-    'x-foo/l2',
     'x-foo/x-bar/k1',
+    'i4',
+    'i5'
   ];
 
   for (var i = 0; i + 1 < elements.length; ++i)
@@ -59,6 +61,6 @@ test(function() {
   elements.reverse();
   for (var i = 0; i + 1 < elements.length; ++i)
       assert_true(shouldNavigateFocus(elements[i], elements[i + 1], 'backward'), elements[i] + ' to ' + elements[i + 1]);
-}, 'Slots tabindex should be considred in focus navigation.');
+}, 'Focus should cover assigned elements of an assigned slot, as well as elements that are directly assigned to a slot.');
 
 </script>