base/numerics: Add explicit cast to SafeUnsignedAbs

This was showing up as a -Wconversion error on gcc, when used via
saturated_cast<int16_t>(...).

Change-Id: Ie643478c1678387ddc4b0386998c77bd74d92700
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008277
Reviewed-by: Justin Schuh <[email protected]>
Commit-Queue: Scott Graham <[email protected]>
Cr-Commit-Position: refs/heads/master@{#734082}
1 file changed