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