Move isRenderedCharacter() to EditorCommand.cpp from Position.cpp

Source/core/editing/commands/EditCommand.h

Index: Source/core/editing/commands/EditCommand.h
diff --git a/Source/core/editing/commands/EditCommand.h b/Source/core/editing/commands/EditCommand.h
index 47bf8231fb0747ddd633c205cf009ed5c557d931..3e2bddbc90453e0fc9f9e73114f161b47a8995cd 100644
--- a/Source/core/editing/commands/EditCommand.h
+++ b/Source/core/editing/commands/EditCommand.h
@@ -63,6 +63,11 @@ protected:
     void setEndingSelection(const VisibleSelection&);
     void setEndingSelection(const VisiblePosition&);
 
+    // TODO(yosin) |isRenderedCharacter()| should be removed, and we should use
+    // |VisiblePosition::characterAfter()| and
+    // |VisiblePosition::characterBefore()|.
+    static bool isRenderedCharacter(const Position&);
+
 private:
     RefPtrWillBeMember<Document> m_document;
     VisibleSelection m_startingSelection;