Port 0a19e449

Original commit message:
    If we do it too early, we might get a constant pool between the reloc info
    and the actual slot.

R=yangguo@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1232123006

Cr-Commit-Position: refs/heads/master@{#29585}