This is a reland of dfdc3135

Original change's description:
> PPC/s390: [interpreter] correctly advance over debug scaling prefixes.
> 
> Port 7a07d74b
> 
> R=yangguo@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
> BUG=
> LOG=N
> 
> Change-Id: I99553fde819cbdc8a12df5b82d9d7230ba4ef8b3
> Reviewed-on: https://chromium-review.googlesource.com/1042355
> Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
> Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
> Cr-Commit-Position: refs/heads/master@{#52970}

Change-Id: I012e79ef5fbff37a8ded8c8cf5d4aaf324cd6ccb
Reviewed-on: https://chromium-review.googlesource.com/1043026Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#52972}