[Android] Update OWNERS information (background_sync)

https://docs.google.com/document/d/19UDqGiQnpkdjvvWpVG8TroXNK0MmhmccU0PkozS8IT0

Bug: 1112872
Change-Id: Id492ddd4d6f645397d22c1aeb96cdd1c1b0e8197
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2340060Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Auto-Submit: Fred Mello <fredmello@chromium.org>
Commit-Queue: Theresa  <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795240}

chrome/android/java/src/org/chromium/chrome/browser/background_sync/OWNERS

@@ -2,3 +2,4 @@ file://chrome/browser/background_sync/OWNERS
 
 # COMPONENT: Blink>BackgroundSync
 # TEAM: platform-capabilities@chromium.org
+# OS: Android

chrome/android/javatests/src/org/chromium/chrome/browser/background_sync/OWNERS

+file://chrome/android/java/src/org/chromium/chrome/browser/background_sync/OWNERS

chrome/android/junit/src/org/chromium/chrome/browser/background_sync/OWNERS

+file://chrome/android/java/src/org/chromium/chrome/browser/background_sync/OWNERS