[MD settings] lighter weight initializer for protocol handler enabled messages

chrome/browser/ui/webui/settings/protocol_handlers_handler.cc

Index: chrome/browser/ui/webui/settings/protocol_handlers_handler.cc
diff --git a/chrome/browser/ui/webui/settings/protocol_handlers_handler.cc b/chrome/browser/ui/webui/settings/protocol_handlers_handler.cc
index 2e9c467140353b24c3a7ced2f1d6e7c56bda7386..a6caac157d440742db10605a9f6cc2367674092c 100644
--- a/chrome/browser/ui/webui/settings/protocol_handlers_handler.cc
+++ b/chrome/browser/ui/webui/settings/protocol_handlers_handler.cc
@@ -43,6 +43,9 @@ void ProtocolHandlersHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback("initializeProtocolHandlerList",
       base::Bind(&ProtocolHandlersHandler::HandleInitializeList,
                  base::Unretained(this)));
+  web_ui()->RegisterMessageCallback("initializeProtocolHandlerUpdates",
+      base::Bind(&ProtocolHandlersHandler::HandleInitializeUpdates,
+                 base::Unretained(this)));
   web_ui()->RegisterMessageCallback("clearDefault",
       base::Bind(&ProtocolHandlersHandler::HandleClearDefault,
                  base::Unretained(this)));
@@ -138,6 +141,12 @@ void ProtocolHandlersHandler::HandleInitializeList(
   UpdateHandlerList();
 }
 
+void ProtocolHandlersHandler::HandleInitializeUpdates(
+    const base::ListValue* args) {
+  AllowJavascript();
+  SendHandlersEnabledValue();
+}
+
 void ProtocolHandlersHandler::SendHandlersEnabledValue() {
   CallJavascriptFunction("cr.webUIListenerCallback",
                          base::StringValue("setHandlersEnabled"),