Add DownloadPDF Callback function.

chrome/renderer/plugins/pdf_plugin_placeholder.h

Index: chrome/renderer/plugins/pdf_plugin_placeholder.h
diff --git a/chrome/renderer/plugins/pdf_plugin_placeholder.h b/chrome/renderer/plugins/pdf_plugin_placeholder.h
index e3975ced1ad65f4060c39cb6a3a648dd40b471b6..39f421677a697dd7ad0f6915bcb6cfc51f22d4b9 100644
--- a/chrome/renderer/plugins/pdf_plugin_placeholder.h
+++ b/chrome/renderer/plugins/pdf_plugin_placeholder.h
@@ -30,6 +30,11 @@ class PDFPluginPlaceholder : public plugins::PluginPlaceholderBase,
 
   // WebViewPlugin::Delegate methods:
   v8::Local<v8::Value> GetV8Handle(v8::Isolate* isolate) final;
+
+  gin::ObjectTemplateBuilder GetObjectTemplateBuilder(
+      v8::Isolate* isolate) final;
+
+  void DownloadPDFCallback();
 };
 
 #endif  // CHROME_RENDERER_PLUGINS_PDF_PLUGIN_PLACEHOLDER_H_