GitLab

Previously the code would dismiss at most one error dialog before or
after running a test. This now loops until no error dialogs are shown.

This should reduce the instance of INJECTION_EVENT failures, but won't
cure them completely.

BUG=399870

Review URL: https://codereview.chromium.org/445503004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287592 0039d316-1c4b-4281-b951-d872f2087c98