Pass method parameters as JavaParamRef in android_webview.

android_webview/native/aw_pdf_exporter.cc

Index: android_webview/native/aw_pdf_exporter.cc
diff --git a/android_webview/native/aw_pdf_exporter.cc b/android_webview/native/aw_pdf_exporter.cc
index 48fa9f991fbf6d830ff74121f6a168b39de43f31..af08f1ff45ef7b44f589debe2bb8a1114a9f5dea 100644
--- a/android_webview/native/aw_pdf_exporter.cc
+++ b/android_webview/native/aw_pdf_exporter.cc
@@ -33,9 +33,9 @@ AwPdfExporter::~AwPdfExporter() {
 }
 
 void AwPdfExporter::ExportToPdf(JNIEnv* env,
-                                jobject obj,
+                                const JavaParamRef<jobject>& obj,
                                 int fd,
-                                jobject cancel_signal) {
+                                const JavaParamRef<jobject>& cancel_signal) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   printing::PrintSettings print_settings;
   InitPdfSettings(env, obj, print_settings);