The RNG state is initialized with random_seed parameter that usually
has lots of zeros. Each random generation iteration shuffles bits with
xor operation over the state. It takes a while before the state is populated
with enough 1s and starts generating uniformly distributed numbers.

The patch warms up the state with 32 iterations when --random_seed is used.

BUG=v8:8265

Change-Id: I7a4e8c842962bea0f2935c7b3673494367d8580f
Reviewed-on: https://chromium-review.googlesource.com/c/1263816
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56418}