Only adding zh-cn to LanguagePolicy if missing.

libraries/Microsoft.Bot.Builder.Dialogs.Adaptive/LanguagePolicy.cs

@@ -77,9 +77,16 @@ private static IDictionary<string, string[]> DefaultPolicy(string[] defaultLangu
             // Locales like zh-CN, zh-TW, etc... are deprecated locales returned by CultureInfo.
             // However, many still supply the old value when setting up WebChat.  Since we
             // really just need the progression to check for LG/LU files, we are manually adding
-            // them so that these files are found.
-            policy.Add("zh-cn", new string[] { "zh-cn", "zh" });
-            policy.Add("zh-tw", new string[] { "zh-tw", "zh" });
+            // them so that these files are found.  This is OS version specific.
+            if (!policy.ContainsKey("zh-cn"))
+            {
+                policy.Add("zh-cn", new string[] { "zh-cn", "zh" });
+            }
+
+            if (!policy.ContainsKey("zh-tw"))
+            {
+                policy.Add("zh-tw", new string[] { "zh-tw", "zh" });
+            }
 
             return policy;
         }