This introduces SilenceNaN operator, which makes sure that we only
store quiet NaNs into holey arrays. We omit the NaN silencing code
at instruction selection time if the input is an operation that
cannot possibly produce signalling NaNs.
BUG=
Review-Url: https://codereview.chromium.org/2060233002
Cr-Commit-Position: refs/heads/master@{#36950}
