Implement a runtime headless mode for Linux

gpu/ipc/service/gpu_init.cc

Index: gpu/ipc/service/gpu_init.cc
diff --git a/gpu/ipc/service/gpu_init.cc b/gpu/ipc/service/gpu_init.cc
index 98620c4ece9ee668c52299a48edb56cb1f6dad09..add75a1472805f8aad92340b8e12135edcccb85e 100644
--- a/gpu/ipc/service/gpu_init.cc
+++ b/gpu/ipc/service/gpu_init.cc
@@ -17,6 +17,7 @@
 #include "gpu/config/gpu_util.h"
 #include "gpu/ipc/service/gpu_watchdog_thread.h"
 #include "gpu/ipc/service/switches.h"
+#include "ui/gfx/switches.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_switches.h"
 #include "ui/gl/init/gl_factory.h"
@@ -127,6 +128,7 @@ bool GpuInit::InitializeAndStartSandbox(const base::CommandLine& command_line) {
   // to run slowly in that case.
   bool enable_watchdog =
       !command_line.HasSwitch(switches::kDisableGpuWatchdog) &&
+      !command_line.HasSwitch(switches::kHeadless) &&
       !RunningOnValgrind();
 
   // Disable the watchdog in debug builds because they tend to only be run by