The C_WASM_ENTRY only calls wasm code, so (outgoing) parameters of this
code are always untagged.

R=ahaas@chromium.org

Bug: v8:7049
Change-Id: I989908eea668bd56aa88f3f1744105d218584ef1
Reviewed-on: https://chromium-review.googlesource.com/758245
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49221}