Port 6d706ae3

Original Commit Message:

    and split Smi out of objects.h into smi.h.

R=jkummerow@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: Id876a65c3e0af550caa246090b60580645faedc5
Reviewed-on: https://chromium-review.googlesource.com/c/1320032Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#57295}