Merge "Remove unnecessary constraint on previous_api"

		validatingNullability :=

			strings.Contains(d.Javadoc.args, "--validate-nullability-from-merged-stubs") ||

				String(d.properties.Validate_nullability_from_list) != ""

		migratingNullability := String(d.properties.Previous_api) != ""

		if !(migratingNullability || validatingNullability) {

			ctx.PropertyErrorf("previous_api",

				"has to be non-empty if annotations was enabled (unless validating nullability)")

		}

		migratingNullability := String(d.properties.Previous_api) != ""

		if migratingNullability {

			previousApi := android.PathForModuleSrc(ctx, String(d.properties.Previous_api))

			cmd.FlagWithInput("--migrate-nullness ", previousApi)