Adds a new test_type 'raw' to run tests on swarming without wrapping it
on gtest-parallel.
This will be used to run webrtc_perf_tests directly.
Bug: chromium:755660
Change-Id: I8558faadf242d1db1ad3e13083941886c92b1bd9
Reviewed-on: https://webrtc-review.googlesource.com/49360
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21962}