Both TestMD5Intrinsics and TestMD5MultiBlockIntrinsics get the expected hash in the first iteration of computing MD5, and this iteration is run by the interpreter.

The tests later run some warm-up iterations and get the hash for comparison. The hash is supposed to be obtained from the intrinsics. However, WARMUP_ITERATIONS is set to 1 in DigestSanityTestBase, and the hash is not obtained from the intrinsics.

Reproduction:
1. Introduce a bug in MacroAssembler::fast_md5 (x86)
#define FF(r1, r2, r3, r4, k, s, t) \
  /*movl(rsi, r3); remove an instruction*/ \
  ...
2. TestMD5Intrinsics still passes.
3. Change WARMUP_ITERATIONS in DigestSanityTestBase to 600.
4. TestMD5Intrinsics fails.