Dialer: allow framework to do dark theming automatically

  <!-- Activities and Applications should inherit from one of the themes above. -->

  <style name="Dialer.ThemeBase">

    <item name="android:forceDarkAllowed">true</item>

    <!-- These values should be used to color all backgrounds. -->

    <item name="android:colorBackground">@color/dialer_background_color</item>

    <item name="android:colorBackgroundFloating">@android:color/white</item>