jni_generator: Make all object-returning natives return ScopedJavaLocalRef.

android_webview/native/aw_settings.cc

Index: android_webview/native/aw_settings.cc
diff --git a/android_webview/native/aw_settings.cc b/android_webview/native/aw_settings.cc
index c0674f511b00f3369a5f0a27772abafbff89382d..a5ae993bc71502b1c1baba606e3a3b09c0f2a18d 100644
--- a/android_webview/native/aw_settings.cc
+++ b/android_webview/native/aw_settings.cc
@@ -429,8 +429,9 @@ static jlong Init(JNIEnv* env,
   return reinterpret_cast<intptr_t>(settings);
 }
 
-static jstring GetDefaultUserAgent(JNIEnv* env, jclass clazz) {
-  return base::android::ConvertUTF8ToJavaString(env, GetUserAgent()).Release();
+static ScopedJavaLocalRef<jstring> GetDefaultUserAgent(JNIEnv* env,
+                                                       jclass clazz) {
+  return base::android::ConvertUTF8ToJavaString(env, GetUserAgent());
 }
 
 bool RegisterAwSettings(JNIEnv* env) {