Add backer@ to components/viz/OWNERS

Change-Id: I82781e8ed5881492b1d9210ec8fa24ae02802c65
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1512926
Reviewed-by: weiliangc <weiliangc@chromium.org>
Reviewed-by: Peng Huang <penghuang@chromium.org>
Commit-Queue: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639510}

components/viz/OWNERS

@@ -21,6 +21,7 @@ weiliangc@chromium.org
 rjkroege@chromium.org
 ccameron@chromium.org
 penghuang@chromium.org
+backer@chromium.org
 
 # display_embedder / ozone
 rjkroege@chromium.org