Fix MultiProfileDownloadNotificationTest.DownloadMultipleFiles flakiness

This test occasionally crashes with the network service enabled because
a request hits the Interceptor after its been deleted.

Change-Id: Ib09e8c6cdf1208ced3297af37e2261c880bae0f1
Reviewed-on: https://chromium-review.googlesource.com/c/1478307
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633809}
1 file changed