[Editing] Modify mostForward/BackwardCaretPosition naming confusion.

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 635cc65accb70b160bb612c63ddae4d901c7af88..884fd59342a29e3d1abd4a60eb2fb8fd72c2170b 100644
--- a/Source/core/editing/Position.cpp
+++ b/Source/core/editing/Position.cpp
@@ -483,13 +483,13 @@ bool PositionAlgorithm<Strategy>::atEndOfTree() const
 template <typename Strategy>
 PositionAlgorithm<Strategy> PositionAlgorithm<Strategy>::upstream(EditingBoundaryCrossingRule rule) const
 {
-    return mostForwardCaretPosition(*this, rule);
+    return mostBackwardCaretPosition(*this, rule);
 }
 
 template <typename Strategy>
 PositionAlgorithm<Strategy> PositionAlgorithm<Strategy>::downstream(EditingBoundaryCrossingRule rule) const
 {
-    return mostBackwardCaretPosition(*this, rule);
+    return mostForwardCaretPosition(*this, rule);
 }
 
 // TODO(yosin) We should move |isVisuallyEquivalentCandidate()| to