Reland "Update BrowsingDataRemoverBrowserTest to include MediaLicenses"

Original change's description:
> MediaLicenses can be cleared from the ClearBrowsingData dialog, so update the
> BrowsingDataRemoverBrowserTest to check them as well. This uses the test-only
> External Clear Key CDM to store the license in the file system, if it is
> available.
>

This reverts commit 72f2d4cd06bcaaad1a8f91a9b7b5559ecf70b8d9.

BUG=808690,879812
TEST=new browser_tests pass

Change-Id: Ie9e9229fc85244eed922d93dce82cb3fa09bbe5c
Reviewed-on: https://chromium-review.googlesource.com/c/1342779
Reviewed-by: Christian Dullweber <dullweber@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609752}