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) &&

[Zhenyao Mo, 2016/12/12 18:21:43]

Can you explain why this is needed?

[Sami, 2016/12/12 20:04:13]

In Linux the watchdog thread has a dependency on the X11 display server, which
won't be there in headless mode. I decided the most straightforward way to deal
with that was to turn the watchdog off, since it doesn't really serve any
purpose in headless mode anyway (we're not currently trying to use any real GPU
there).

       !RunningOnValgrind();
 
   // Disable the watchdog in debug builds because they tend to only be run by