Add dark theme bg for transient taskbar.

Bug: 256052691
Test: enable dark theme, view dark taskbar
      disable dark theme, view light taskbar

Change-Id: Icf8b946fd68804a904493336063704a6584d5f0e
diff --git a/res/color-night-v31/transient_taskbar_background.xml b/res/color-night-v31/transient_taskbar_background.xml
new file mode 100644
index 0000000..40f6494
--- /dev/null
+++ b/res/color-night-v31/transient_taskbar_background.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2022 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+  <item android:color="@android:color/system_neutral1_500" android:lStar="15" />
+</selector>
+