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Tracing can generate large output files (over 50M) especially if system
tracing is enabled, and are very compressible. Add an option to compress
them using the same machinery that chrome://tracing uses.

This also uses less /tmp space to store the stream. Storing large files
in /tmp was causing problems for chromecast, as space is /tmp is very
limited.

BUG=791708

Change-Id: Icbaac91cccb825a305431569bf6f42011d3cfbea
Reviewed-on: https://chromium-review.googlesource.com/807384
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521939}