Fix several ineffective integer overflow checks

Commit edd4a76e (which addressed bugs 15328708, 15342615, 15342751) added
several integer overflow checks. Unfortunately, those checks fail to take into
account integer promotion rules and are thus themselves subject to an integer
overflow. Cast the sizeof() operator to a uint64_t to force promotion while
multiplying.

Bug: 20139950
Change-Id: Ieb29a170edb805c722fc5658935f2390003e5260