Introduce composed tree version of leftPositionOf()

Source/core/editing/VisiblePosition.cpp

Index: Source/core/editing/VisiblePosition.cpp
diff --git a/Source/core/editing/VisiblePosition.cpp b/Source/core/editing/VisiblePosition.cpp
index cb21338f0154b64ef559e8e89aad4647a06f5d6c..3de66608f932bfae4c59cb1b5944033441590b91 100644
--- a/Source/core/editing/VisiblePosition.cpp
+++ b/Source/core/editing/VisiblePosition.cpp
@@ -93,6 +93,11 @@ VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTree
     return VisiblePositionInComposedTree::create(PositionInComposedTreeWithAffinity(position, affinity));
 }
 
+VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTreeWithAffinity& positionWithAffinity)
+{
+    return VisiblePositionInComposedTree::create(positionWithAffinity);
+}
+
 VisiblePosition createVisiblePositionInDOMTree(const Position& position, TextAffinity affinity)
 {
     return createVisiblePosition(position, affinity);