Create a User for the test profile in externalfile URL unittests.

With DriveFS enabled, a User is required for the test Profile so ensure
one is created. Creating the User causes the filesystem names to include
the username hash, so update externalfile URLs in the test to include
it.

Change-Id: I25f9205dd2deab1878da3ca0e21f5ede08279968
Reviewed-on: https://chromium-review.googlesource.com/c/1408733
Reviewed-by: Sergei Datsenko <dats@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622387}
2 files changed