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- This CL includes only the skeleton code to open an empty app from
  chrome://print-management.
- The app and browsertests are in Polymer3.
- Includes basic browsertest to test if app is loaded correctly.
- Future CL will set this app as an System Web App.
- This app is hidden behind a feature flag by default.

Bug: 1053704
Test: browsertest

Change-Id: I777c9912568e10621d763be50052f830fa63e765
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2066878Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: jimmy gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748293}