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 0f5c61e8f8e3fdc86ddb1fc005c45ded4438d1e8..0aca886cbbe5eca36fb970bc2c372b25f84d3103 100644
--- a/headless/lib/headless_content_main_delegate.h
+++ b/headless/lib/headless_content_main_delegate.h
@@ -23,6 +23,7 @@ namespace headless {
 
 class HeadlessBrowserImpl;
 class HeadlessContentBrowserClient;
+class HeadlessContentRendererClient;
 
 // Exported for tests.
 class HEADLESS_EXPORT HeadlessContentMainDelegate
@@ -39,6 +40,7 @@ class HEADLESS_EXPORT HeadlessContentMainDelegate
       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(); }
 
@@ -56,6 +58,7 @@ class HEADLESS_EXPORT HeadlessContentMainDelegate
   static HeadlessContentMainDelegate* GetInstance();
 
   std::unique_ptr<HeadlessContentBrowserClient> browser_client_;
+  std::unique_ptr<HeadlessContentRendererClient> renderer_client_;
   HeadlessContentClient content_client_;
   HeadlessPlatformEventSource platform_event_source_;