Revert "Webkit: add to support file uploading"

This reverts commit 667938a112c1a793ed897896cbe60657f136955f.
Revert "Harden against transiently unavailable backup transports"

This reverts commit 7ddf1e71cb1e547a567a62dae717ed9f6cccfb06.
Revert "Handle backup transport registration dynamically"

This reverts commit 1a9386913a10affedd810417fbd2d29372a3a5cb.