splash: Default to dark color background for splashscreen.

The default background color for splashscreen is the 'light' color,
which is white. This can cause an unexpected white flash during a
few use cases. So fix this by defaulting to the 'dark' background
color (black).

Bug: 273080885
Test: remove location access to maps, relaunch maps.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:88dd1d3bea401647e3f2b5edcb4a5178f4aa9a0a)
Merged-In: Ib9d5c840ee8f0ddd931525b64d451f8af1a1e1cd
Change-Id: Ib9d5c840ee8f0ddd931525b64d451f8af1a1e1cd

libs/WindowManager/Shell/res/values-watch/colors.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/*
+ * Copyright 2020, 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.
+ */
+-->
+<resources>
+    <color name="splash_window_background_default">@color/splash_screen_bg_dark</color>
+</resources>
+