[Media Router] Add OWNERS file for Android remote playback metrics.

This adds an OWNERS file for this folder for consistency with other
Android code that supports Cast features.

Change-Id: I7da7aac04b56c493cf78be47afdfc2e47604682e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441528Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814296}

chrome/android/java/src/org/chromium/chrome/browser/media/remote/OWNERS

+file://components/media_router/browser/android/OWNERS

components/media_router/OWNERS

@@ -2,4 +2,5 @@ mfoltz@chromium.org
 btolsch@chromium.org
 takumif@chromium.org
 
+# TEAM: media-dev@chromium.org
 # COMPONENT: Internals>Cast