Add DownloadPDF Callback function.

chrome/renderer/plugins/pdf_plugin_placeholder.cc

Index: chrome/renderer/plugins/pdf_plugin_placeholder.cc
diff --git a/chrome/renderer/plugins/pdf_plugin_placeholder.cc b/chrome/renderer/plugins/pdf_plugin_placeholder.cc
index 3263551c8f9bbf9fb0f54b346856ffb04d9ffba5..82dcdd4022438fb13d18a5f7c277ada118b47be6 100644
--- a/chrome/renderer/plugins/pdf_plugin_placeholder.cc
+++ b/chrome/renderer/plugins/pdf_plugin_placeholder.cc
@@ -5,6 +5,7 @@
 #include "chrome/renderer/plugins/pdf_plugin_placeholder.h"
 
 #include "chrome/grit/renderer_resources.h"
+#include "gin/object_template_builder.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/base/webui/jstemplate_builder.h"
 
@@ -31,3 +32,17 @@ PDFPluginPlaceholder* PDFPluginPlaceholder::CreatePDFPlaceholder(
 v8::Local<v8::Value> PDFPluginPlaceholder::GetV8Handle(v8::Isolate* isolate) {
   return gin::CreateHandle(isolate, this).ToV8();
 }
+
+gin::ObjectTemplateBuilder PDFPluginPlaceholder::GetObjectTemplateBuilder(
+    v8::Isolate* isolate) {
+  gin::ObjectTemplateBuilder builder =
+      gin::Wrappable<PDFPluginPlaceholder>::GetObjectTemplateBuilder(isolate)
+          .SetMethod<void (PDFPluginPlaceholder::*)()>(
+              "downloadPDF", &PDFPluginPlaceholder::DownloadPDFCallback);
+
+  return builder;

[tommycli, 2017/07/05 19:46:23]

I think you can just return it directly like here:
https://cs.chromium.org/chromium/src/components/plugins/renderer/plugin_place...

[amberwon, 2017/07/05 19:54:02]

Done.

+}
+
+void PDFPluginPlaceholder::DownloadPDFCallback() {
+  // TODO(amberwon): Download PDF.

[tommycli, 2017/07/05 19:46:23]

TODO(amberwon): Implement starting PDF download.

[amberwon, 2017/07/05 19:54:02]

Done.

+}