Add permission to modify user preferred display mode.

This permission will be used for testing purposes to modify the user
prefrred mode.

Ignore-AOSP-First: There are merge conflicts in master. So uploading to
master.

Bug: 198452789
Test: m
Change-Id: Id17e20f93ca9db4a24245e8c38f62d95b4f0f4ce
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 7f0c5d4..7d06620 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -460,6 +460,9 @@
     <!-- Permission needed for CTS test - MatchContentFrameRateTest -->
     <uses-permission android:name="android.permission.MODIFY_REFRESH_RATE_SWITCHING_TYPE" />
 
+    <!-- Permission needed for CTS test - DefaultDisplayModeTest -->
+    <uses-permission android:name="android.permission.MODIFY_USER_PREFERRED_DISPLAY_MODE" />
+
     <!-- Permissions needed for CTS test - TimeManagerTest -->
     <uses-permission android:name="android.permission.MANAGE_TIME_AND_ZONE_DETECTION" />
     <uses-permission android:name="android.permission.SUGGEST_EXTERNAL_TIME" />