Pass method parameters as JavaParamRef in android_webview.

android_webview/native/aw_pdf_exporter.h

Index: android_webview/native/aw_pdf_exporter.h
diff --git a/android_webview/native/aw_pdf_exporter.h b/android_webview/native/aw_pdf_exporter.h
index f2513f82b2fde4d952795bd32f7852ced13a1565..2b44a850db5fc090156fcc5088e3f4f354af536b 100644
--- a/android_webview/native/aw_pdf_exporter.h
+++ b/android_webview/native/aw_pdf_exporter.h
@@ -31,9 +31,9 @@ class AwPdfExporter {
   ~AwPdfExporter();
 
   void ExportToPdf(JNIEnv* env,
-                   jobject obj,
+                   const base::android::JavaParamRef<jobject>& obj,
                    int fd,
-                   jobject cancel_signal);
+                   const base::android::JavaParamRef<jobject>& cancel_signal);
 
  private:
   void InitPdfSettings(JNIEnv* env,