Fix HTML help on Mac.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@11041 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/html/helpfrm.cpp

@@ -347,7 +347,11 @@ bool wxHtmlHelpFrame::Create(wxWindow* parent, wxWindowID id,
             wxLayoutConstraints *b4 = new wxLayoutConstraints;
             m_ContentsBox = new wxTreeCtrl(dummy, wxID_HTML_TREECTRL,
                                            wxDefaultPosition, wxDefaultSize,
-                                           wxTR_HAS_BUTTONS | wxSUNKEN_BORDER);
+#ifdef __WXMAC__
+       wxSUNKEN_BORDER|wxTR_MAC_BUTTONS|wxTR_NO_LINES|wxTR_ROW_LINES );
+#else
+       wxSUNKEN_BORDER|wxTR_HAS_BUTTONS );
+#endif
             m_ContentsBox->AssignImageList(ContentsImageList);
 
             b4->top.Below (m_Bookmarks, 10);