Add switchable theme to tuner

Allows option in tuner to switch between system theme overlays
if multiple exist. Requires a restart to take effect.

Test: Settings -> Tuner -> Other -> Theme
Change-Id: Iea43b9cbb67fd91c6008be594ad4cfd19c3f57ec
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 3dea051..0f7b5a5 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -3130,6 +3130,12 @@
     <permission android:name="android.permission.MANAGE_AUTO_FILL"
         android:protectionLevel="signature" />
 
+    <!-- Allows an app to set the theme overlay in /vendor/overlay
+         being used.
+         @hide  <p>Not for use by third-party applications.</p> -->
+    <permission android:name="android.permission.MODIFY_THEME_OVERLAY"
+                android:protectionLevel="signature" />
+
     <application android:process="system"
                  android:persistent="true"
                  android:hasCode="false"