Return (16,16) as the default list icons size in wxMSW.

The standard size of the small icons in list controls under MSW is
traditionally 16*16 so return this from wxMSW wxArtProvider.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68850 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/artmsw.cpp

@@ -124,6 +124,10 @@ wxSize wxArtProvider::GetNativeSizeHint(const wxArtClient& client)
     {
         return wxSize(16, 16);
     }
+    else if (client == wxART_LIST)
+    {
+        return wxSize(16, 16);
+    }
 
     return wxDefaultSize;
 }