Make sure Base URI is encrypted if the document is before using it

Otherwise we may be being targetted by a link content exfiltration
6 jobs for base_uri_exfiltration in 3 minutes and 29 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #1277926
build

00:03:06

passed #1277931
build_android

00:00:52

passed #1277927
build_clang_libcpp

00:03:29

passed #1277930
build_clazy

00:02:33

passed #1277929
build_mingw64_fedora

00:02:22

passed #1277928
build_ubuntu_16_04

00:01:38