There was a bug in WebAssembly.instantiate in the case where a CSP
disallows WebAssembly compilation. In this case the promise returned by
WebAssembly.instantiate was rejected immediately because of the CSP,
but then compilation was started anyways, and the promise was resolved
after compilation for a second time, which caused the crash. With this
CL we do not start compilation if CSP disallows WebAssembly compilation.

R=clemensh@chromium.org

Bug: chromium:881978
Change-Id: Iffdb3e02c3006eb7f86211ab197f81cf20438f0e
Reviewed-on: https://chromium-review.googlesource.com/1219706
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55788}