This assertion was useful for debugging the initial implementation but it
is becoming an issue in tryjobs where tests will hang instead of fail due
to driver bugs.

BUG=angleproject:882

Change-Id: Ib23a0d16dfe250ea175a166b5e277bf07d80a2fa
Reviewed-on: https://chromium-review.googlesource.com/307460
Tryjob-Request: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>