Add --headless flag to Windows

headless/public/headless_browser.cc

Index: headless/public/headless_browser.cc
diff --git a/headless/public/headless_browser.cc b/headless/public/headless_browser.cc
index caa24e794d9a5e553e756bf59c315659c33c8fca..614901acb934c867b95b092f3c52f3c1c5ba8dda 100644
--- a/headless/public/headless_browser.cc
+++ b/headless/public/headless_browser.cc
@@ -9,6 +9,10 @@
 #include "content/public/common/user_agent.h"
 #include "headless/public/version.h"
 
+#if defined(OS_WIN)
+#include "sandbox/win/src/sandbox_types.h"
+#endif
+
 using Options = headless::HeadlessBrowser::Options;
 using Builder = headless::HeadlessBrowser::Options::Builder;
 
@@ -100,6 +104,18 @@ Builder& Builder::AddMojoServiceName(const std::string& mojo_service_name) {
   return *this;
 }
 
+#if defined(OS_WIN)
+Builder& Builder::SetInstance(HINSTANCE instance) {
+  options_.instance = instance;
+  return *this;
+}
+
+Builder& Builder::SetSandboxInfo(sandbox::SandboxInterfaceInfo* sandbox_info) {
+  options_.sandbox_info = sandbox_info;
+  return *this;
+}
+#endif  // defined(OS_WIN)
+
 Builder& Builder::SetUserDataDir(const base::FilePath& user_data_dir) {
   options_.user_data_dir = user_data_dir;
   return *this;