Add --headless flag to Windows

headless/public/headless_shell.h

Index: headless/public/headless_shell.h
diff --git a/headless/public/headless_shell.h b/headless/public/headless_shell.h
index 0fd9066a80d5ef01842a9decea1c10e04b67503c..783f4ba4994fde5c20d8ecb629f02d4b5ed8cc62 100644
--- a/headless/public/headless_shell.h
+++ b/headless/public/headless_shell.h
@@ -7,11 +7,21 @@
 
 #include "headless/public/headless_export.h"
 
+#if defined(OS_WIN)
+#include "sandbox/win/src/sandbox_types.h"
+#endif
+
 namespace headless {
 
 // Start the Headless Shell application. Intended to be called early in main().
 // Returns the exit code for the process.
+#if defined(OS_WIN)
+HEADLESS_EXPORT int HeadlessShellMain(
+    HINSTANCE instance,
+    sandbox::SandboxInterfaceInfo* sandbox_info);
+#else
 HEADLESS_EXPORT int HeadlessShellMain(int argc, const char** argv);
+#endif  // defined(OS_WIN)
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_HEADLESS_SHELL_H_