Fix remoting NM hosts to verify that incoming messages are dictionaries.

remoting/host/it2me/it2me_native_messaging_host.cc

Index: remoting/host/it2me/it2me_native_messaging_host.cc
diff --git a/remoting/host/it2me/it2me_native_messaging_host.cc b/remoting/host/it2me/it2me_native_messaging_host.cc
index 6fb65df5ec7548a40489fdd78c90cec94bd21009..35d578a7aa2abfde251f31ef9f3ecf42beee01ef 100644
--- a/remoting/host/it2me/it2me_native_messaging_host.cc
+++ b/remoting/host/it2me/it2me_native_messaging_host.cc
@@ -87,6 +87,12 @@ void It2MeNativeMessagingHost::Start(const base::Closure& quit_closure) {
 void It2MeNativeMessagingHost::OnMessage(scoped_ptr<base::Value> message) {
   DCHECK(task_runner()->BelongsToCurrentThread());
 
+  if (message->GetType() != base::Value::TYPE_DICTIONARY) {
+    LOG(ERROR) << "Received a message that's not a dictionary.";
+    channel_->SendMessage(nullptr);
+    return;
+  }
+
   scoped_ptr<base::DictionaryValue> message_dict(
       static_cast<base::DictionaryValue*>(message.release()));
   scoped_ptr<base::DictionaryValue> response(new base::DictionaryValue());