When the backend sees an Int64Constant in a translation, this currently
indicates the value is a Smi value.

Bug: v8:8015
Change-Id: I1527a6374b395d3a33ae0339df4b563084ea678e
Reviewed-on: https://chromium-review.googlesource.com/1226593Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55916}