jni_generator: Pass object parameters as JavaParamRef.

chrome/browser/android/document/document_web_contents_delegate.cc

 // Copyright 2015 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 "chrome/browser/android/document/document_web_contents_delegate.h"
 
 #include "components/web_contents_delegate_android/web_contents_delegate_android.h"
 #include "content/public/browser/web_contents.h"
 #include "jni/DocumentWebContentsDelegate_jni.h"
 
@@ skipping 37 matching lines @@
     int main_frame_route_id,
     WindowContainerType window_container_type,
     const std::string& frame_name,
     const GURL& target_url,
     const std::string& partition_id,
     content::SessionStorageNamespace* session_storage_namespace) {
   NOTREACHED();
   return false;
 }
 
-
-static jlong Initialize(JNIEnv* env, jobject obj) {
+static jlong Initialize(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   return reinterpret_cast<intptr_t>(new DocumentWebContentsDelegate(env, obj));
 }