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..ebb25a152ab51132c6f8ea2ed689da3bf0b91572 100644
--- a/Source/core/dom/shadow/ComposedTreeTraversal.cpp
+++ b/Source/core/dom/shadow/ComposedTreeTraversal.cpp
@@ -241,4 +241,18 @@ unsigned ComposedTreeTraversal::countChildren(const Node& node)
     return count;
 }
 
+Node* ComposedTreeTraversal::lastWithin(const Node& current)
+{

[hayato, 2015/03/26 03:28:27]

Could you insert assertions like other public functions do?
I'd like to make sure all public functions assert the input and the output.

[hajimehoshi, 2015/03/26 03:43:26]

Done.

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