Introduce PositionInComposedTree version of enclosingBlock()

Source/core/editing/EditingUtilities.cpp

Index: Source/core/editing/EditingUtilities.cpp
diff --git a/Source/core/editing/EditingUtilities.cpp b/Source/core/editing/EditingUtilities.cpp
index 3f77c55442fdec4f8213018f66ab2777f843384c..48881234e34683800878fa2cf55acccdb475cefc 100644
--- a/Source/core/editing/EditingUtilities.cpp
+++ b/Source/core/editing/EditingUtilities.cpp
@@ -661,12 +661,23 @@ Element* enclosingBlock(Node* node, EditingBoundaryCrossingRule rule)
     return enclosingBlock(firstPositionInOrBeforeNode(node), rule);
 }
 
-Element* enclosingBlock(const Position& position, EditingBoundaryCrossingRule rule)
+template <typename Strategy>
+Element* enclosingBlockAlgorithm(const PositionAlgorithm<Strategy>& position, EditingBoundaryCrossingRule rule)
 {
     Node* enclosingNode = enclosingNodeOfType(position, isEnclosingBlock, rule);
     return enclosingNode && enclosingNode->isElementNode() ? toElement(enclosingNode) : nullptr;
 }
 
+Element* enclosingBlock(const Position& position, EditingBoundaryCrossingRule rule)
+{
+    return enclosingBlockAlgorithm<EditingStrategy>(position, rule);
+}
+
+Element* enclosingBlock(const PositionInComposedTree& position, EditingBoundaryCrossingRule rule)
+{
+    return enclosingBlockAlgorithm<EditingInComposedTreeStrategy>(position, rule);
+}
+
 Element* enclosingBlockFlowElement(Node& node)
 {
     if (isBlockFlowElement(node))