jni_generator: Pass object parameters as JavaParamRef.

mandoline/app/android/mandoline_activity.cc

Index: mandoline/app/android/mandoline_activity.cc
diff --git a/mandoline/app/android/mandoline_activity.cc b/mandoline/app/android/mandoline_activity.cc
index f7e19f689a02804bc66cd1c080179bddf641be83..0d05724fcf4b00c2cf22a0ca7bc8cea70cd516ee 100644
--- a/mandoline/app/android/mandoline_activity.cc
+++ b/mandoline/app/android/mandoline_activity.cc
@@ -10,7 +10,9 @@
 
 namespace mandoline {
 
-static void LaunchURL(JNIEnv* env, jclass clazz, jstring jurl) {
+static void LaunchURL(JNIEnv* env,
+                      const JavaParamRef<jclass>& clazz,
+                      const JavaParamRef<jstring>& jurl) {
   LaunchHandlerPtr launch_handler;
   mojo::runner::GetContext()->application_manager()->ConnectToService(
       GURL("mojo:phone_ui"), &launch_handler);