The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3

commit b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3
Author: Noel Gordon <noel@chromium.org>
Date: Mon Nov 26 01:08:48 2018

Closure compile drive_sync_handler externs file and its mock file

Add drive sync handler externs file to the Closure build, and "fix" up
Closure compile issues. Make DriveSyncHandler an interface and use new
type DriveSyncHandlerImpl for the concrete implementation. Add a BUILD
rule for mock_drive_sync_handler and fix Closure compile issues.

Actions model unittest defined MockDriveSyncHandler methods.  Move the
methods to mock_drive_sync_handler and update the actions model test.

Bug:  908045 
Change-Id: I6b150f13f47e3b6263b16a1faefa0a1342cb36bb
Reviewed-on: https://chromium-review.googlesource.com/c/1349509
Reviewed-by: Stuart Langley <slangley@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610747}
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/externs/background/drive_sync_handler.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/BUILD.gn
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/background.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/drive_sync_handler.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/drive_sync_handler_unittest.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/media_import_handler.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/background/js/mock_drive_sync_handler.js
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/foreground/js/actions_model_unittest.html
[modify] https://crrev.com/b2e8acdc23a1dc6b8b496a334a2e692230c7c3b3/ui/file_manager/file_manager/foreground/js/actions_model_unittest.js