Use !== instead of !=.

Bug: 
Change-Id: I3f8127d54b80973f9ea7bb6ddf25afd928cb3045
Reviewed-on: https://chromium-review.googlesource.com/753733Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Franziska Hinkelmann <franzih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49210}