Add alancutter as hosted_app_* OWNER for chrome/browser/ui/extensions

Change-Id: I35304eb77e8e09d971b1854416c121bc5ec0935e
Reviewed-on: https://chromium-review.googlesource.com/1212369Reviewed-by: Ben Wells <benwells@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589436}

chrome/browser/ui/extensions/OWNERS

 # App-y stuff
 benwells@chromium.org
+per-file hosted_app_*=alancutter@chromium.org
 per-file hosted_app_*=mgiuca@chromium.org
 per-file hosted_app_*=ortuno@chromium.org