GitLab

Move PrintBackendServiceTestImpl into its own files instead of being
bundled with PrintBackendBrowserTest.  This will enable it to be reused
by other forthcoming tests.

Add helper functions for launching the service.

Add ability to register a test service to be used in place of launching
out-of-process instances on-demand by regular production code.

This has no change to existing test coverage or behavior.

Bug: 809738
Change-Id: I74c596b3284e69d6eabd525eb77e5f6e8f8b0c05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631326Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Alan Screen <awscreen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846393}