Move inRenderedText() to VisibleUnits.cpp from Position.cpp

Source/core/editing/Position.h

Index: Source/core/editing/Position.h
diff --git a/Source/core/editing/Position.h b/Source/core/editing/Position.h
index 6efb38b4600c3780f0b0d1d240a90b045cb7bf8c..b6dec6faec8576217a631246c545af3f08ce37b5 100644
--- a/Source/core/editing/Position.h
+++ b/Source/core/editing/Position.h
@@ -407,11 +407,6 @@ inline PositionInComposedTree fromPositionInDOMTree<EditingInComposedTreeStrateg
     return toPositionInComposedTree(position);
 }
 
-// TODO(yosin) We should move |inRenderedText()| to "VisibleUnits.h" for
-// reduce dependency of |LayoutObject| in |Position| class.
-CORE_EXPORT bool inRenderedText(const Position&);
-CORE_EXPORT bool inRenderedText(const PositionInComposedTree&);
-
 CORE_EXPORT int uncheckedPreviousOffset(const Node*, int current);
 CORE_EXPORT int uncheckedNextOffset(const Node*, int current);