[Upstream] Force instantiation of BSKSF during unit tests
Call EnsureBrowserStateKeyedServiceFactoriesBuilt() during initialisation of
"chrome_ios_unittests" to ensure the BSKSF are correctly registered against
the DependencyManager before launching the tests.
Call ios::RegisterPathProvider() before running the tests so that they can
use the iOS specific paths by name.
BUG=468694
R=droger@chromium.org
Review URL: https://codereview.chromium.org/
1111193002
Cr-Commit-Position: refs/heads/master@{#327461}