add print to pdf for headless

headless/lib/headless_content_main_delegate.h

Index: headless/lib/headless_content_main_delegate.h
diff --git a/headless/lib/headless_content_main_delegate.h b/headless/lib/headless_content_main_delegate.h
index cb33f226d178bf684b7c7f54894b97bf07381b36..be70e0018a6886c714900d095e8cb794a620db87 100644
--- a/headless/lib/headless_content_main_delegate.h
+++ b/headless/lib/headless_content_main_delegate.h
@@ -22,6 +22,7 @@ namespace headless {
 
 class HeadlessBrowserImpl;
 class HeadlessContentBrowserClient;
+class HeadlessContentRendererClient;
 
 class HeadlessContentMainDelegate : public content::ContentMainDelegate {
  public:
@@ -36,6 +37,7 @@ class HeadlessContentMainDelegate : public content::ContentMainDelegate {
       const std::string& process_type,
       const content::MainFunctionParams& main_function_params) override;
   content::ContentBrowserClient* CreateContentBrowserClient() override;
+  content::ContentRendererClient* CreateContentRendererClient() override;
 
   HeadlessBrowserImpl* browser() const { return browser_.get(); }
 
@@ -53,6 +55,7 @@ class HeadlessContentMainDelegate : public content::ContentMainDelegate {
   static HeadlessContentMainDelegate* GetInstance();
 
   std::unique_ptr<HeadlessContentBrowserClient> browser_client_;
+  std::unique_ptr<HeadlessContentRendererClient> renderer_client_;
   HeadlessContentClient content_client_;
   HeadlessPlatformEventSource platform_event_source_;