cros: Add weidongg and newcomer to ash/app_list OWNERS

Add weidongg@ and newcomer@ to ash/app_list OWNERS after talking to
xiyuan@.

Change-Id: Icee73a00b2354cd2a7b1d29475d1620dfe1fefbf
Reviewed-on: https://chromium-review.googlesource.com/1195893
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587336}

ash/app_list/OWNERS

 calamity@chromium.org
 jennyz@chromium.org
 khmel@chromium.org
+newcomer@chromium.org
 stevenjb@chromium.org
+weidongg@chromium.org
 xiyuan@chromium.org