[net][websocket] Allow http/https scheme and relative URLs

Bug: chromium:1379162
Change-Id: Ib06ed270a064ea80a7ccc44f252c478d2d635016
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5060558


Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1281895}