Templatize canonicalizeCandidate() in VisiblePosition

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 046f5b6883f9c9c47e687b62db901d27e73890bd..76cdecdeae20823bf738628fe401a75a214cae96 100644
--- a/Source/core/editing/VisiblePosition.cpp
+++ b/Source/core/editing/VisiblePosition.cpp
@@ -542,12 +542,13 @@ VisiblePosition VisiblePosition::skipToEndOfEditingBoundary(const VisiblePositio
     return firstEditableVisiblePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
 }
 
-static Position canonicalizeCandidate(const Position& candidate)
+template <typename PositionType>
+static PositionType canonicalizeCandidate(const PositionType& candidate)
 {
     if (candidate.isNull())
-        return Position();
+        return PositionType();
     ASSERT(candidate.isCandidate());
-    Position upstream = candidate.upstream();
+    PositionType upstream = candidate.upstream();
     if (upstream.isCandidate())
         return upstream;
     return candidate;