The special treatment is not required anymore because the wasm spec
changed and NaNs do not have to be preserved anymore. In addition, it
may introduce non-determinism which confused the fuzzers.

R=titzer@chromium.org
BUG=chromium:681033

Review-Url: https://codereview.chromium.org/2630293002
Cr-Commit-Position: refs/heads/master@{#42359}