Addresses failures with the following, in some files:
-Wshorten-64-to-32
-Wimplicit-int-conversion
-Wsign-compare
-Wsign-conversion
-Wtautological-unsigned-zero-compare

(This specific CL focuses on tests.)

Bug: chromium:1292951
PiperOrigin-RevId: 473055916
Change-Id: I40cdd6c87ba9d0a5fb2db5746cff04f14ee829c2