ES6 collections: Fix order of constructor logic

ES6 collections: Fix order of constructor logic

The adder should be gotten before the iterator.

Motivation: Once this is done we should be able to use a for-of loop
instead which leads to cleaner code and correct behavior once the
for-of loop correctly supports abrupt completion.

BUG=None
LOG=N
R=adamk

Committed: https://crrev.com/36e72aedf073a78915c5412e77499dbe98878766
Cr-Commit-Position: refs/heads/master@{#26803}

[arv (Not doing code reviews), 2015-02-23 17:07:22]

cleanup

[arv (Not doing code reviews), 2015-02-23 17:07:54]

PTAL

[adamk, 2015-02-23 18:17:53]

lgtm

[arv (Not doing code reviews), 2015-02-23 18:53:35]

The CQ bit was checked by arv@chromium.org

[commit-bot: I haz the power, 2015-02-23 18:54:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/949933002/20001

[commit-bot: I haz the power, 2015-02-23 18:55:38]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-02-23 18:55:39]

Failed to apply the patch.

[commit-bot: I haz the power, 2015-02-23 18:55:41]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-23 18:55:54]

Patchset 2 (id:??) landed as
https://crrev.com/36e72aedf073a78915c5412e77499dbe98878766
Cr-Commit-Position: refs/heads/master@{#26803}