Revert "Revert "Rm special-casing for root URLs of mobile sites""

This reverts commit af75ae60548cf99266665c7fae5f0c6a2967df83

Change-Id: I76721456934a96e010439b744e781fdedc679eb1
Merge "Revert "Revert "Rm special-casing for root URLs of mobile sites""" into production