Block leakage of urls in sandbox iframes: Preventing url base fallback leakage...

Block leakage of urls in sandbox iframes: Preventing url base fallback leakage in cross orgin sandbox iframe (#1447)

DO NOT ACTIVATE: the patch is a wip

Addition of the ""block-url-leakage-sandbox-iframe" flag disabled by default.
The aim is to understand whether it is possible to disable the
leakage of certain information in sandbox iframes