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- Add overview of how perf builders, testers, and processors work
- Add tip on how to debug tests

Bug: chromium:1143048
Change-Id: Iebb8c72b47a5ef1dbc5c9171e3fa7148ebb202b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2503652
Commit-Queue: Ryan Heise <heiserya@google.com>
Auto-Submit: Ryan Heise <heiserya@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821765}