GitLab

Add ability to wait for the given events into
ExtensionForceInstallMixin:
* the pref gets updated;
* the extension's background page is loaded for the first time.

Migrate the tests in
challenge_response_auth_keys_loader_browsertest.cc onto
ExtensionForceInstallMixin (instead of
TestCertificateProviderExtensionLoginScreenMixin).

Bug: 1090941
Change-Id: I2b71546564b99a682a74fef70abc243d3e198c8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2312640
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Omar Morsi <omorsi@google.com>
Reviewed-by: Fabian Sommer <fabiansommer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791215}