At the moment, WebAssembly.instantiate(bytes) is implemented by
desugaring it to WebAssembly.compile(bytes).then(WebAssembly.instantiate).
The problem is that the {then} in this snippet is observable. With this
CL I introduce a CompilationResultResolver which allows to do the
desugaring internally and thereby make the {then} unobservable.
Unfortunately the result of WebAssembly.instantiate(bytes) is different
than the result of WebAssembly.instantiate(module). Therefore I also
introduced an InstantiationResultResolver for symmetry with
WebAssembly.compile.

R=mstarzinger@chromium.org
Bug: chromium:837417

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I2d98e03d65f2ada19041d5a9e2df5da91b24ccca
Reviewed-on: https://chromium-review.googlesource.com/1059783
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53347}