Even after https://codereview.chromium.org/2371963002 we might still
create JSTypedArray instances where the length field is a HeapNumber,
especially when TurboFan no longer canonicalizes all values in Smi
range to Smis (which we try to achieve currently). This adds strict
checking for this fact now.

R=mstarzinger@chromium.org

Review-Url: https://codereview.chromium.org/2373013002
Cr-Commit-Position: refs/heads/master@{#39771}