Implement a runtime headless mode for Linux

chrome/app/chrome_main.cc

Index: chrome/app/chrome_main.cc
diff --git a/chrome/app/chrome_main.cc b/chrome/app/chrome_main.cc
index e24c4675287833e7a2654dccbe050ebe1dc89f10..cefe93b2e9bdf78db8f1739abaa27c1c6655e41e 100644
--- a/chrome/app/chrome_main.cc
+++ b/chrome/app/chrome_main.cc
@@ -5,13 +5,15 @@
 #include <stdint.h>
 
 #include "build/build_config.h"
+#include "base/command_line.h"
 #include "base/time/time.h"
 #include "chrome/app/chrome_main_delegate.h"
 #include "chrome/common/features.h"
 #include "content/public/app/content_main.h"
+#include "content/public/common/content_switches.h"
+#include "headless/app/headless_shell.h"
 
 #if BUILDFLAG(ENABLE_PACKAGE_MASH_SERVICES)
-#include "base/command_line.h"
 #include "chrome/app/mash/mash_runner.h"
 #include "chrome/common/channel_info.h"
 #include "components/version_info/version_info.h"
@@ -58,6 +60,11 @@ int ChromeMain(int argc, const char** argv) {
 #if defined(OS_WIN)
   install_static::InstallDetails::InitializeFromPrimaryModule(
       chrome::kChromeElfDllName);
+
+  const base::CommandLine command_line(argc, argv);
+#if defined(OS_LINUX)
+  if (command_line.HasSwitch(switches::kHeadless))
+    return HeadlessShellMain(argc, argv);
 #endif
 
   ChromeMainDelegate chrome_main_delegate(
@@ -98,8 +105,6 @@ int ChromeMain(int argc, const char** argv) {
   version_info::Channel channel = chrome::GetChannel();
   if (channel == version_info::Channel::CANARY ||
       channel == version_info::Channel::UNKNOWN) {
-    const base::CommandLine& command_line =
-        *base::CommandLine::ForCurrentProcess();
     if (command_line.HasSwitch("mash"))
       return MashMain();
   }