jni_generator: Pass object parameters as JavaParamRef.

content/browser/android/content_readback_handler.cc

Index: content/browser/android/content_readback_handler.cc
diff --git a/content/browser/android/content_readback_handler.cc b/content/browser/android/content_readback_handler.cc
index 6ff62e43c0706ac797c26f170eac81f4669aae52..568b7d3de6a06197ea86d908fd8c1f13ad05f3be 100644
--- a/content/browser/android/content_readback_handler.cc
+++ b/content/browser/android/content_readback_handler.cc
@@ -115,7 +115,7 @@ void ContentReadbackHandler::OnFinishReadback(int readback_id,
 }
 
 // static
-static jlong Init(JNIEnv* env, jobject obj) {
+static jlong Init(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   ContentReadbackHandler* content_readback_handler =
       new ContentReadbackHandler(env, obj);
   return reinterpret_cast<intptr_t>(content_readback_handler);