Reland "[Logging] Disable always-log-ERRORs-to-stderr unless LOG_TO_FILE is set."

This is a reland of ffa05b99247df703a03b472f6d7b1fa0f3f23582

logging::LogMessage has a special-case to write LOG_ERROR messages
to stderr, even if LOG_TO_STDERR is not enabled, to make ERROR and
FATAL messages more visible, especially in tests.

Restrict this behaviour to apply only when no log destinations are
set, other than LOG_TO_FILE, so that binaries which only
LOG_TO_SYSTEM_DEBUG_LOG will never emit logspam to stderr.

Tested by adding a unit test for this case.

Bug: 968387
Change-Id: Ibe3369eb2a47accdd17cd3cbb19c921de827ca70
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704917
Reviewed-by: danakj <[email protected]>
Commit-Queue: Wez <[email protected]>
Auto-Submit: Wez <[email protected]>
Cr-Commit-Position: refs/heads/master@{#678513}
2 files changed