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}