Revert "Ignore to show splash screen if the decorView is not opaque"

This reverts commit 877a2da3.

Reason for revert: As b/172991922#comment12, in case app launch performance regression happens when ignored non-opaque splash screen. (e.g camera app).

Bug: 146080233
Change-Id: Ided765479ef042e7bedf6fccb1fedfe4ddbc87af