Move honorEditingBoundaryAtOr{Before,After}() for VisiblePosition to VisibleUnits.cpp

Source/core/editing/VisiblePosition.h

Index: Source/core/editing/VisiblePosition.h
diff --git a/Source/core/editing/VisiblePosition.h b/Source/core/editing/VisiblePosition.h
index 1422ef15ba57df6eefaca4e9ccc33dab9eb69f09..302c10b2ee9d80b5895e588f4e7b6ca9cb3b7bd8 100644
--- a/Source/core/editing/VisiblePosition.h
+++ b/Source/core/editing/VisiblePosition.h
@@ -109,14 +109,6 @@ private:
     TextAffinity m_affinity;
 };
 
-// TODO(yosin) We should move |honorEditingBoundaryAtOr{Before,After} to
-// "VisibleUnits.cpp" as static function.
-// next() and previous() will increment/decrement by a character cluster.
-VisiblePosition honorEditingBoundaryAtOrBefore(const VisiblePosition&, const Position& anchor);
-PositionWithAffinity honorEditingBoundaryAtOrBeforeOf(const PositionWithAffinity&, const Position& anchor);
-PositionInComposedTreeWithAffinity honorEditingBoundaryAtOrBeforeOf(const PositionInComposedTreeWithAffinity&, const PositionInComposedTree& anchor);
-VisiblePosition honorEditingBoundaryAtOrAfter(const VisiblePosition&, const Position& anchor);
-
 CORE_EXPORT VisiblePosition createVisiblePosition(const Position&, TextAffinity = VP_DEFAULT_AFFINITY);
 CORE_EXPORT VisiblePosition createVisiblePosition(const PositionWithAffinity&);
 CORE_EXPORT VisiblePosition createVisiblePosition(const PositionInComposedTree&, TextAffinity = VP_DEFAULT_AFFINITY);