This makes {Script} objects created for WebAssembly no longer reference
a concrete instance object, but a module object instead. All uses of the
field in question only require module-wide information and the script is
meant to represent the set of all instances, not just one concrete
instance.

R=clemensh@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I751d4b75c8a970cffcb1a37b6c22ff69e9ee5489
Reviewed-on: https://chromium-review.googlesource.com/1043871Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53002}