This will replace "<?>" in certain debug output with the empty string.
There should be no end-user visible changes, though.

Change-Id: I80db2f2169532c600662977025185378004f7cd5
Reviewed-on: https://chromium-review.googlesource.com/1213188
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55742}