GitLab

Add a flag to DnsUdpTracker to signify "low entropy" (setting that flag
in non-test is TODO for a subsequent CL).  Rework DNS attempt code to
allow using TCP instead of UDP when that flag is set.

Bug: 1093361
Change-Id: I74e935e0ddf2a76112222e395b6b1c7e6bf469bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2340281Reviewed-by: Dan McArdle <dmcardle@chromium.org>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795726}