Move parentEditingBoundary() to VisibileUnits.cpp from Position.cpp.

Source/core/editing/Position.cpp

Index: Source/core/editing/Position.cpp
diff --git a/Source/core/editing/Position.cpp b/Source/core/editing/Position.cpp
index 6935d5d4597b37a658904a87ed5fd5cad98d3c13..a2d7a5969e43609785fe3fa09985797a9a7438c0 100644
--- a/Source/core/editing/Position.cpp
+++ b/Source/core/editing/Position.cpp
@@ -463,41 +463,6 @@ static bool atEditingBoundary(const PositionAlgorithm<Strategy> positions)
 }
 
 template <typename Strategy>
-static ContainerNode* nonShadowBoundaryParentNode(Node* node)
-{
-    ContainerNode* parent = Strategy::parent(*node);
-    return parent && !parent->isShadowRoot() ? parent : nullptr;
-}
-
-template <typename Strategy>
-static Node* parentEditingBoundaryAlgorithm(const PositionAlgorithm<Strategy>& position)
-{
-    Node* const anchorNode = position.anchorNode();
-    if (!anchorNode)
-        return nullptr;
-
-    Node* documentElement = anchorNode->document().documentElement();
-    if (!documentElement)
-        return nullptr;
-
-    Node* boundary = position.computeContainerNode();
-    while (boundary != documentElement && nonShadowBoundaryParentNode<Strategy>(boundary) && anchorNode->hasEditableStyle() == Strategy::parent(*boundary)->hasEditableStyle())
-        boundary = nonShadowBoundaryParentNode<Strategy>(boundary);
-
-    return boundary;
-}
-
-Node* parentEditingBoundary(const Position& position)
-{
-    return parentEditingBoundaryAlgorithm<EditingStrategy>(position);
-}
-
-Node* parentEditingBoundary(const PositionInComposedTree& position)
-{
-    return parentEditingBoundaryAlgorithm<EditingInComposedTreeStrategy>(position);
-}
-
-template <typename Strategy>
 bool PositionAlgorithm<Strategy>::atStartOfTree() const
 {
     if (isNull())