We can avoid the ToString conversion before doing the HasProperty check.
This avoid a costly Smi to String conversion which is unecessary for the
following lookups.
For very large dictionary elements this is a significant slow down as we
will no longer hit the GetNumberStringCache.

Change-Id: I5a0eb13470ab3d3d8a87ee36d28ce7be5cbc2b2e
Reviewed-on: https://chromium-review.googlesource.com/626056Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47574}