Remove DayNight themes from public API (again)

Bug: 22628106
Change-Id: Id55c9e626813c70671a93aedf8b1e0cdaed45ec1
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 189ed33..fb5f21a 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -141,6 +141,14 @@
             "com.android.server.MountService$Lifecycle";
     private static final String PERSISTENT_DATA_BLOCK_PROP = "ro.frp.pst";
 
+    /**
+     * Default theme used by the system context. This is used to style
+     * system-provided dialogs, such as the Power Off dialog, and other
+     * visual content.
+     */
+    private static final int DEFAULT_SYSTEM_THEME =
+            com.android.internal.R.style.Theme_Material_DayNight_DarkActionBar;
+
     private final int mFactoryTestMode;
     private Timer mProfilerSnapshotTimer;
 
@@ -320,7 +328,7 @@
     private void createSystemContext() {
         ActivityThread activityThread = ActivityThread.systemMain();
         mSystemContext = activityThread.getSystemContext();
-        mSystemContext.setTheme(android.R.style.Theme_Material_DayNight_DarkActionBar);
+        mSystemContext.setTheme(DEFAULT_SYSTEM_THEME);
     }
 
     /**