webrtc/api/stats/OWNERS file added.

hbos and hta are already OWNERS of webrtc/stats/ and of rtcstats* files
(per-file rtcstats*=) in webrtc/api/. When the webrtc/api/stats/ folder
was created we forgot to add this OWNERS file (per-file OWNERS does not
apply to subfolders apparently).

BUG=chromium:627816
NOTRY=True

Review-Url: https://codereview.webrtc.org/2392633002
Cr-Commit-Position: refs/heads/master@{#14482}

webrtc/api/stats/OWNERS

@@ -0,0 +1,9 @@
+hbos@webrtc.org
+hta@webrtc.org
+
+# These are for the common case of adding or renaming files. If you're doing
+# structural changes, please get a review from a reviewer in this file.
+per-file *.gn=*
+per-file *.gni=*
+per-file *.gyp=*
+per-file *.gypi=*