Ports https://codereview.chromium.org/1671753002

It brings auth support (so developers can use 'isolate' if
they really want to) and adds *.pyc to default isolate
blacklist.

TBR=maruel@chromium.org,  vadimsh@chromium.org, stip@chromium.org
BUG=584073
LOG=n

Review URL: https://codereview.chromium.org/1677453002

Cr-Commit-Position: refs/heads/master@{#33763}