Determine the checkbox size in wxGetGridCheckBoxRect() itself

It doesn't make much sense to pass the size to the function supposed to
compute it, so call wxRendererNative::GetCheckBoxSize() from the
function itself instead of forcing its callers to do it.

No real changes.

include/wx/generic/private/grid.h

@@ -1007,12 +1007,16 @@ private:
     wxGridDataTypeInfoArray m_typeinfo;
 };
 
-// Returns the rect of the check box in a cell with the given alignmens
-// and the size.
-// The function is used by wxGridCellBoolEditor and wxGridCellBoolRenderer.
-wxRect wxGetGridCheckBoxRect(const wxSize& checkBoxSize,
-                             const wxRect& cellRect,
-                             int hAlign, int vAlign);
+// Returns the rectangle for showing a check box in a cell with the given
+// alignment.
+//
+// The function is used by wxGridCellBoolEditor and wxGridCellBoolRenderer to
+// draw a check mark and position wxCheckBox respectively.
+wxRect
+wxGetGridCheckBoxRect(wxWindow* win,
+                      const wxRect& cellRect,
+                      int hAlign,
+                      int vAlign);
 
 #endif // wxUSE_GRID
 #endif // _WX_GENERIC_GRID_PRIVATE_H_