The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/761e2f979c1d11df39cef5ef7f1e1842e6c0aada

commit 761e2f979c1d11df39cef5ef7f1e1842e6c0aada
Author: Noel Gordon <noel@chromium.org>
Date: Tue Nov 27 02:53:26 2018

Make ProgressCenter externs file an @interface

 - change ProgressCenter externs file to be an @interface class
 - rename background page ProgressCenter to ProgressCenterImpl,
   and make it @implement the {ProgressCenter} interface
 - use ProgressCenterImpl as the implementation for Files App.
 - make MockProgressCenter @implement ProgressCenter for tests
 - add missing ProgressCenter methods to MockProgressCenter to
   make it Closure compile.
 - BUILD rules for progress_center, and mock_progress_center,
   were added in CL:1349139, and CL:1349147, respectively.

No change in test behavior, no new tests.

Bug:  908379 
Change-Id: I087b72abce9221d464761724e3fcf2ccdb2dfad5
Reviewed-on: https://chromium-review.googlesource.com/c/1350563
Reviewed-by: Stuart Langley <slangley@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611005}
[modify] https://crrev.com/761e2f979c1d11df39cef5ef7f1e1842e6c0aada/ui/file_manager/externs/background/progress_center.js
[modify] https://crrev.com/761e2f979c1d11df39cef5ef7f1e1842e6c0aada/ui/file_manager/file_manager/background/js/background.js
[modify] https://crrev.com/761e2f979c1d11df39cef5ef7f1e1842e6c0aada/ui/file_manager/file_manager/background/js/mock_progress_center.js
[modify] https://crrev.com/761e2f979c1d11df39cef5ef7f1e1842e6c0aada/ui/file_manager/file_manager/background/js/progress_center.js