Added documentation

DNN Platform/HttpModules/Localization/LocalizationModule.cs

@@ -24,8 +24,15 @@ public void Dispose()
             // intentionally left empty
         }
 
+        /// <summary>
+        /// The PreRequestHandlerExecute event happens after AuthenticateRequest. This means this code will
+        /// run after we know the identity of the user. This allows for the accurate retrieval of the locale
+        /// which depends not just on the site and page locale, but also on the user's preference.
+        /// </summary>
         private static void Context_PreRequestHandlerExecute(object sender, EventArgs e)
         {
+            // We need to ensure that we don't run this code when not requesting a page as otherwise we may not have
+            // an accurate portal identified (e.g. resources)
             var isPage = HttpContext.Current.CurrentHandler is Framework.PageBase;
             if (!isPage)
             {
@@ -38,6 +45,8 @@ private static void Context_PreRequestHandlerExecute(object sender, EventArgs e)
                 return;
             }
 
+            // The portalSettings should always be correct at this point, but in case we can't find a portal
+            // we need to insure we're not setting the thread locale.
             var portalSettings = PortalController.Instance.GetCurrentSettings();
             if (portalSettings != null)
             {