Clear the system bars color when removing the splash screen window.

There can reset the system bars color once the splash screen window is
going to be removed, so the real system bars color can be
controlled by app, without waiting for the reveal animation.
Also clear this effect when transfer splash screen to client, so client
can control the color on their own.

Bug: 196550450
Test: verify no status bar color changed when playing reveal animation.
Change-Id: Ibb353d350fa2921188c8c4b54f8e029ee3869c16