Make SetDisplayPower() take a callback to signal completion

chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc

Index: chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc
diff --git a/chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc b/chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc
index 9fc1718809e6b5ab4207787c3367ea960c9da52c..57269d99437ac0d2ee259c40636ef0442c136663 100644
--- a/chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc
+++ b/chrome/browser/chromeos/dbus/chrome_display_power_service_provider_delegate.cc
@@ -19,7 +19,8 @@ ChromeDisplayPowerServiceProviderDelegate::
 }
 
 void ChromeDisplayPowerServiceProviderDelegate::SetDisplayPower(
-    DisplayPowerState power_state) {
+    DisplayPowerState power_state,
+    const ResponseCallback& callback) {
   // Turning displays off when the device becomes idle or on just before
   // we suspend may trigger a mouse move, which would then be incorrectly
   // reported as user activity.  Let the UserActivityDetector
@@ -27,7 +28,7 @@ void ChromeDisplayPowerServiceProviderDelegate::SetDisplayPower(
   ui::UserActivityDetector::Get()->OnDisplayPowerChanging();
 
   ash::Shell::GetInstance()->display_configurator()->SetDisplayPower(
-      power_state, ui::DisplayConfigurator::kSetDisplayPowerNoFlags);
+      power_state, ui::DisplayConfigurator::kSetDisplayPowerNoFlags, callback);
 }
 
 void ChromeDisplayPowerServiceProviderDelegate::SetDimming(bool dimmed) {