Refactor and simplify wxChoice::DoGetBestSize().

Use wxTextMeasure instead of duplicating its code and also reuse the code
between different ports.

Closes #14706.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72848 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/choice.h

@@ -58,6 +58,13 @@ public:
     // override wxItemContainer::IsSorted
     virtual bool IsSorted() const { return HasFlag(wxCB_SORT); }
 
+protected:
+    // The generic implementation doesn't determine the height correctly and
+    // doesn't account for the width of the arrow but does take into account
+    // the string widths, so the derived classes should override it and set the
+    // height and add the arrow width to the size returned by this version.
+    virtual wxSize DoGetBestSize() const;
+
 private:
     wxDECLARE_NO_COPY_CLASS(wxChoiceBase);
 };