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..8a781b758fc8bd5525a019a8572416755eb154fd 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 {
@@ -486,6 +487,8 @@ PowerSaveBlocker::PowerSaveBlocker(
                              blocking_task_runner)),
       ui_task_runner_(ui_task_runner),
       blocking_task_runner_(blocking_task_runner) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless))

[hashimoto, 2017/01/17 02:08:12]

1. Instead of adding if to the ctor and the dtor, please modify
PowerSaveBlocker::Delegate::SelectAPI() above to return NO_API
2. I'm not familiar with base::nix::GetDesktopEnvironment(), but shouldn't it
detect it when X11 is not available?
3. Do we really want to always disable poser save blocker when running headless?

[Sami, 2017/01/17 13:44:29]

Good idea, done. (Note that I had to do the same to the X screensaver related
code.)
Looks like it doesn't check for X11 as such, which I think is correct since not
all the detected environments actually require X11.
I believe so. There's no API we could use to control power saving so the blocker
can't really do anything in the first place.

+    return;
   delegate_->Init();
 
   if (type == kPowerSaveBlockPreventDisplaySleep) {
@@ -497,6 +500,8 @@ PowerSaveBlocker::PowerSaveBlocker(
 }
 
 PowerSaveBlocker::~PowerSaveBlocker() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless))
+    return;
   delegate_->CleanUp();
   if (freedesktop_suspend_delegate_)
     freedesktop_suspend_delegate_->CleanUp();