[simd.js] Set --harmony-simd flag in test config.

[simd.js] Set --harmony-simd flag in test config.
Adds the flag to the test configuration so we aren't just testing the
polyfill.
Fixes some number conversion in native fromFloat32x4 function that now
fails.

LOG=N
BUG=v8:4124
Committed: https://crrev.com/2090c08d3ebafbabf5e2a85a58d605d60cbf6650
Cr-Commit-Position: refs/heads/master@{#30341}

[bbudge, 2015-08-24 20:57:32]

bbudge@chromium.org changed reviewers:
+ dehrenberg@chromium.org

[Dan Ehrenberg, 2015-08-24 21:01:02]

littledan@chromium.org changed reviewers:
+ littledan@chromium.org

[Dan Ehrenberg, 2015-08-24 21:01:03]

lgtm

Yay for testing!

[bbudge, 2015-08-24 21:08:21]

The CQ bit was checked by bbudge@chromium.org

[commit-bot: I haz the power, 2015-08-24 21:08:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1312703003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1312703003/1

[commit-bot: I haz the power, 2015-08-24 21:18:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-24 21:19:17]

Patchset 1 (id:??) landed as
https://crrev.com/2090c08d3ebafbabf5e2a85a58d605d60cbf6650
Cr-Commit-Position: refs/heads/master@{#30341}