Display off is done by a callback into backlight controller

powerd_unittest.cc

Index: powerd_unittest.cc
diff --git a/powerd_unittest.cc b/powerd_unittest.cc
index 448ea1d4c4e94cac3b5d422dac5fc8f771f499b2..279fda4196663503b04eaadf69f3a0f82888dd92 100644
--- a/powerd_unittest.cc
+++ b/powerd_unittest.cc
@@ -59,6 +59,7 @@ class DaemonTest : public Test {
         .WillOnce(DoAll(SetArgumentPointee<0>(kDefaultBrightness),
                         SetArgumentPointee<1>(kMaxBrightness),
                         Return(true)));
+    EXPECT_CALL(backlight_, SetScreenOffFunc(NotNull(), NotNull()));
     prefs_.SetInt64(kPluggedBrightnessOffset, kPluggedBrightness);
     prefs_.SetInt64(kUnpluggedBrightnessOffset, kUnpluggedBrightness);
     prefs_.SetInt64(kAlsBrightnessLevel, kAlsBrightness);