Port 4eff883b
     c72b49bd

Original commit message:
    Ideally we would not need the StoreWriteBarrier instructions at all,
    but represent the RecordWrite functionality as machine subgraph, but
    that'll take some time to get there. In the mean time we can have a
    shorter instruction sequence by recognizing immediate indices here.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1695333002

Cr-Commit-Position: refs/heads/master@{#34006}