Remove implicit conversions from scoped_refptr to T* in mojo/

mojo/dbus/dbus_external_service.cc

Index: mojo/dbus/dbus_external_service.cc
diff --git a/mojo/dbus/dbus_external_service.cc b/mojo/dbus/dbus_external_service.cc
index 65b4bf122a57eab2440eb97447b9c2a8903b2e1e..6b8d722959930825bdb6b8e794e58bfb1ce9165e 100644
--- a/mojo/dbus/dbus_external_service.cc
+++ b/mojo/dbus/dbus_external_service.cc
@@ -67,7 +67,7 @@ void DBusExternalServiceBase::ExportMethods() {
 }
 
 void DBusExternalServiceBase::InitializeDBus() {
-  CHECK(!bus_);
+  CHECK(!bus_.get());
   dbus::Bus::Options options;
   options.bus_type = dbus::Bus::SESSION;
   bus_ = new dbus::Bus(options);