port 1e00bb57 (r30737).

original commit message:

    (reason for revert/reland: patch incorrectly left --vector-stores flag
     on, helpfully revealing some gcstress issues to look at, but they
     don't need to block this CL).

    Some pretty hacky code was used to carry out the tail-call
    handler dispatch on ia32 vector stores due to a lack
    of free registers. It really tanks performance. A better
    approach is to use a virtual register on the isolate.

BUG=

Review URL: https://codereview.chromium.org/1344383002

Cr-Commit-Position: refs/heads/master@{#30781}