power save blocker: Don't try to block power saving in headless mode

device/power_save_blocker/power_save_blocker_x11.cc

Index: device/power_save_blocker/power_save_blocker_x11.cc
diff --git a/device/power_save_blocker/power_save_blocker_x11.cc b/device/power_save_blocker/power_save_blocker_x11.cc
index 286e042b9bd588f93515a6820beaecace9ee8532..0063acc24cfb3c2c64932c39ccdeffbf3a029ee8 100644
--- a/device/power_save_blocker/power_save_blocker_x11.cc
+++ b/device/power_save_blocker/power_save_blocker_x11.cc
@@ -32,6 +32,7 @@
 #include "dbus/message.h"
 #include "dbus/object_path.h"
 #include "dbus/object_proxy.h"
+#include "ui/gfx/switches.h"
 #include "ui/gfx/x/x11_types.h"
 
 namespace {
@@ -436,6 +437,8 @@ bool PowerSaveBlocker::Delegate::DPMSEnabled() {
 
 bool PowerSaveBlocker::Delegate::XSSAvailable() {
   DCHECK(ui_task_runner_->RunsTasksOnCurrentThread());
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless))

[hashimoto, 2017/01/17 15:28:32]

Please add a brief comment to justify this behavior.

[Sami, 2017/01/17 15:43:49]

Done.

+    return false;
   XDisplay* display = gfx::GetXDisplay();
   int dummy;
   int major;
@@ -452,6 +455,8 @@ bool PowerSaveBlocker::Delegate::XSSAvailable() {
 
 DBusAPI PowerSaveBlocker::Delegate::SelectAPI() {
   DCHECK(ui_task_runner_->RunsTasksOnCurrentThread());
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless))

[hashimoto, 2017/01/17 15:28:32]

ditto.

[Sami, 2017/01/17 15:43:49]

Done.

+    return NO_API;
   std::unique_ptr<base::Environment> env(base::Environment::Create());
   switch (base::nix::GetDesktopEnvironment(env.get())) {
     case base::nix::DESKTOP_ENVIRONMENT_GNOME: