Add custom tabs team as owners for SplitCompatCustomTabsService.java

Requested by peconn@ in http://crrev.com/c/2462176.

Bug: 1126301
Change-Id: Id5d18fbefa553655e0a28db63c9cc64b1231d39d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462173
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815623}

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

+per-file SplitCompatCustomTabsService.java=file://chrome/browser/android/customtabs/OWNERS