[test] Run all variants on TSAN bots.

Bug: chromium:773214
Change-Id: I7ebcbea3152a506e3ed569ef975413321c937dc6
Reviewed-on: https://chromium-review.googlesource.com/708755Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48441}

tools/run-tests.py

@@ -589,13 +589,10 @@ def ProcessOptions(options):
     VARIANTS = EXHAUSTIVE_VARIANTS
 
   # TODO(machenbach): Figure out how to test a bigger subset of variants on
-  # msan and tsan.
+  # msan.
   if options.msan:
     VARIANTS = ["default"]
 
-  if options.tsan:
-    VARIANTS = ["default"]
-
   if options.j == 0:
     options.j = multiprocessing.cpu_count()