Implement a runtime headless mode for Linux

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 6aa3e5e4ea7f632217da2043ec7c46cb4308da87..3931330f9d96abc159f0627eab8a9d9f3cef47b7 100644
--- a/headless/lib/headless_content_main_delegate.h
+++ b/headless/lib/headless_content_main_delegate.h
@@ -10,6 +10,7 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/app/content_main_delegate.h"
+#include "headless/lib/browser/headless_platform_event_source.h"
 #include "headless/lib/headless_content_client.h"
 
 namespace headless {
@@ -49,6 +50,7 @@ class HeadlessContentMainDelegate : public content::ContentMainDelegate {
   std::unique_ptr<HeadlessContentRendererClient> renderer_client_;
   std::unique_ptr<HeadlessContentUtilityClient> utility_client_;
   HeadlessContentClient content_client_;
+  HeadlessPlatformEventSource platform_event_source_;
 
   std::unique_ptr<HeadlessBrowserImpl> browser_;