We cannot eliminate unused CheckFloat64Hole nodes, since loading from a
holey array can have side-effects, i.e. triggering getters in the
prototype chain.

R=mvstanton@chromium.org
BUG=chromium:686737

Review-Url: https://codereview.chromium.org/2665123002
Cr-Commit-Position: refs/heads/master@{#42806}