GitLab

Fall back to reading from urandom only when that fails.

This is a re-land of
https://chromium-review.googlesource.com/c/chromium/src/+/1762604, which was
reverted in https://chromium-review.googlesource.com/c/chromium/src/+/2377418.

Bug: 995996
Change-Id: I007581630f789881ab956c1b1666b99f087fa154
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2380673Reviewed-by: Julien Tinnes <jln@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Chris Palmer <palmer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802691}