Show anonymous acquisition experiment once regardless of page load.

Change-Id: I0300c7f27a599343bd75495a59b93e0d3cf607ba
(cherry picked from commit e4c79ddb9f3cc940dd4e86c5a72db10bfc4cdc95)
Localisation updates from https://translatewiki.net.

Change-Id: I8b50d36aeca138671f45ab06ead9f22f984d7271
(cherry picked from commit 9629ebb6e62abacc8597010a703f8a2515f73900)