Make Xianzhu a cc/OWNER

Change-Id: Idb32f317aadba2d4480bd5d01034ac3e45f86d76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869720
Auto-Submit: Philip Rogers <pdr@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707553}

cc/OWNERS

@@ -9,6 +9,7 @@
 enne@chromium.org
 danakj@chromium.org
 pdr@chromium.org
+wangxianzhu@chromium.org
 
 # mac-specific
 ccameron@chromium.org
@@ -30,6 +31,7 @@ flackr@chromium.org
 chrishtr@chromium.org
 weiliangc@chromium.org
 pdr@chromium.org
+wangxianzhu@chromium.org
 
 # animation
 flackr@chromium.org