Reland of Fix FlatTreeTraversal for a slot in a document tree

third_party/WebKit/Source/core/dom/shadow/FlatTreeTraversalTest.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/shadow/FlatTreeTraversal.h"
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Node.h"
@@ skipping 553 matching lines @@
   EXPECT_EQ(d112, FlatTreeTraversal::previous(*d6));
 
   EXPECT_EQ(d11, FlatTreeTraversal::parent(*d111));
   EXPECT_EQ(d11, FlatTreeTraversal::parent(*d112));
   EXPECT_EQ(d11, FlatTreeTraversal::parent(*d2));
   EXPECT_EQ(d11, FlatTreeTraversal::parent(*d14));
   EXPECT_EQ(nullptr, FlatTreeTraversal::parent(*d3));
   EXPECT_EQ(nullptr, FlatTreeTraversal::parent(*d4));
 }
 
+TEST_F(FlatTreeTraversalTest, v1SlotInDocumentTree) {
+  const char* mainHTML =
+      "<div id='parent'>"
+      "<slot>"
+      "<div id='child1'></div>"
+      "<div id='child2'></div>"
+      "</slot>"
+      "</div>";
+
+  setupDocumentTree(mainHTML);
+  Element* body = document().body();
+  Element* parent = body->querySelector("#parent");
+  Element* child1 = body->querySelector("#child1");
+  Element* child2 = body->querySelector("#child2");
+
+  EXPECT_EQ(child1, FlatTreeTraversal::firstChild(*parent));
+  EXPECT_EQ(child2, FlatTreeTraversal::nextSibling(*child1));
+  EXPECT_EQ(nullptr, FlatTreeTraversal::nextSibling(*child2));
+  EXPECT_EQ(parent, FlatTreeTraversal::parent(*child1));
+  EXPECT_EQ(parent, FlatTreeTraversal::parent(*child2));
+}
+
 }  // namespace blink