Lights out.

Not yet wired up to FLAG_FULLSCREEN; right now you must
invoke it manually by longpressing on the clock area.

Bug: 2905073
Change-Id: I43a005f2e4c08edb3673aef523bcaa1e088e8a71

packages/SystemUI/proguard.flags

@@ -2,4 +2,5 @@
   public void notificationIconsClicked(android.view.View);
   public void systemInfoClicked(android.view.View);
   public void recentButtonClicked(android.view.View);
+  public void toggleLightsOut(android.view.View);
 }