Add file_manager OWNERS to drive_internals page

Add OWNERS in file://ui/file_manager/OWNERS to drive_internals page,
since this is mainly used for debugging issues with the Drive Sync
engine which is primarly used by the file manager.

Bug: 845065
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Iff904ccc44c163621f620fa930e838697f4f8f1e
Reviewed-on: https://chromium-review.googlesource.com/1075837Reviewed-by: Satoru Takabayashi <satorux@google.com>
Reviewed-by: Satoru Takabayashi <satorux@chromium.org>
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Commit-Queue: Sasha Morrissey <sashab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565568}

chrome/browser/resources/chromeos/OWNERS

@@ -6,5 +6,4 @@ stevenjb@chromium.org
 xiyuan@chromium.org
 zelidrag@chromium.org
 
-per-file drive_internals*=hashimoto@chromium.org
-per-file drive_internals*=kinaba@chromium.org
+per-file drive_internals*=file://ui/file_manager/OWNERS

chrome/browser/ui/webui/chromeos/OWNERS

@@ -6,5 +6,4 @@ xiyuan@chromium.org
 zelidrag@chromium.org
 
 per-file network*=stevenjb@chromium.org
-per-file drive_internals_ui.*=hashimoto@chromium.org
-per-file drive_internals_ui.*=kinaba@chromium.org
+per-file drive_internals_ui.*=file://ui/file_manager/OWNERS