GitLab

The flag for specifying the URL for the Data Saver secure proxy check
was changed in https://codereview.chromium.org/961983002/. This change
makes the relevant integration test use the new flag value, and also
makes the test restart after each page.

BUG=463210

Review URL: https://codereview.chromium.org/971073002

Cr-Commit-Position: refs/heads/master@{#318923}