jni_generator: Pass object parameters as JavaParamRef.

chrome/browser/android/appmenu/app_menu_drag_helper.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/histogram_macros.h"
 #include "chrome/browser/android/appmenu/app_menu_drag_helper.h"
 #include "jni/AppMenuDragHelper_jni.h"
 
 bool RegisterAppMenuDragHelper(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 // static
-void RecordAppMenuTouchDuration(JNIEnv* env, jclass jcaller, jlong time_ms) {
+void RecordAppMenuTouchDuration(JNIEnv* env,
+                                const JavaParamRef<jclass>& jcaller,
+                                jlong time_ms) {
   UMA_HISTOGRAM_TIMES("WrenchMenu.TouchDuration",
                       base::TimeDelta::FromMilliseconds(time_ms));
 }