browser test failure on Windows (debug)

[bsclifton]

Description

Browser test failure unintentionally introduced with brave/brave-core#3154

Steps to Reproduce

1. Be on Windows
2. Check out master
3. Do debug build
4. Run browser tests with npm run test brave_browser_tests

Actual result:

BraveProfilePrefsBrowserTest.AdvancedShieldsExistingUserValue fails:

[8784:8388:0819/155955.361:FATAL:thread_restrictions.cc(76)] Check failed: !g_blocking_disallowed.Get().Get(). Function marked as blocking was called from a scope that disallows blocking! If this task is running inside the ThreadPool, it needs to have MayBlock() in its TaskTraits. Otherwise, consider making this blocking work asynchronous or, as a last resort, you may use ScopedAllowBlocking (see its documentation for best practices).
g_blocking_disallowed currently set to true by

Expected result:

No failures

Reproduces how often:

100%