jni_generator: Pass object parameters as JavaParamRef.

chrome/browser/android/metrics/variations_session.cc

Index: chrome/browser/android/metrics/variations_session.cc
diff --git a/chrome/browser/android/metrics/variations_session.cc b/chrome/browser/android/metrics/variations_session.cc
index 663233aa3b1b979b27f30452e8a61fe70ceae08d..79b75a88c2f698854465ac29094c343b7927ae63 100644
--- a/chrome/browser/android/metrics/variations_session.cc
+++ b/chrome/browser/android/metrics/variations_session.cc
@@ -17,9 +17,10 @@ bool g_on_app_enter_foreground_called = false;
 
 }  // namespace
 
-static void StartVariationsSession(JNIEnv* env,
-                                   jobject obj,
-                                   jstring jrestrict_mode) {
+static void StartVariationsSession(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& obj,
+    const JavaParamRef<jstring>& jrestrict_mode) {
   DCHECK(g_browser_process);
 
   chrome_variations::VariationsService* variations_service =