GitLab

Adds preferences for configuring the tracing mode and enabled tracing
categories to the mobile tracing preferences.

Bug: 898512
Change-Id: I23583dd24868918ce29eebce68568344b7c3c2f0
Binary-Size: feature implementation, strings will not be translated.
Reviewed-on: https://chromium-review.googlesource.com/c/1340300
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609657}