Add ComposedTreeTraversal::lastWithin/lastWithinOrSelf

Source/core/dom/shadow/ComposedTreeTraversal.cpp

Index: Source/core/dom/shadow/ComposedTreeTraversal.cpp
diff --git a/Source/core/dom/shadow/ComposedTreeTraversal.cpp b/Source/core/dom/shadow/ComposedTreeTraversal.cpp
index 8966b8faf5431cd71aa70284474b6687d23da9be..b8ce9dcd46bf1155b1b4e1b88e6cb2eb20ff9e38 100644
--- a/Source/core/dom/shadow/ComposedTreeTraversal.cpp
+++ b/Source/core/dom/shadow/ComposedTreeTraversal.cpp
@@ -241,4 +241,20 @@ unsigned ComposedTreeTraversal::countChildren(const Node& node)
     return count;
 }
 
+Node* ComposedTreeTraversal::lastWithin(const Node& current)
+{
+    assertPrecondition(current);
+    Node* descendant = lastChild(current);

[hayato, 2015/03/26 03:48:44]

Could you use travrseLastChild instead of lastChild() in this function?

And insert assertPostCondtion(descendant) at last.

[hajimehoshi, 2015/03/26 03:56:11]

Done.

Besides, renamed |current| to |node| for consistency.

+    for (Node* child = descendant; child; child = lastChild(*child))
+        descendant = child;
+    return descendant;
+}
+
+Node& ComposedTreeTraversal::lastWithinOrSelf(const Node& current)
+{
+    assertPrecondition(current);
+    Node* lastDescendant = ComposedTreeTraversal::lastWithin(current);
+    return lastDescendant ? *lastDescendant : const_cast<Node&>(current);
+}
+
 } // namespace