Add methods to extras' InternalPackedArray

Add methods to extras' InternalPackedArray

https://codereview.chromium.org/1343113003 introduced a separate InternalPackedArray constructor to the extras utils object, distinct from the one used by natives. However, it omitted the code to set up the methods for that InternalPackedArray. This makes all the basic manipulation methods available.

BUG=v8:4276
LOG=Y
R=jochen@chromium.org,yangguo@chromium.org

Committed: https://crrev.com/8f8457d2a414b1cdad6dc3cecff062a8ff5649cb
Cr-Commit-Position: refs/heads/master@{#31272}

[domenic, 2015-10-13 22:08:07]

Open to alternate suggestions on how to approach this (e.g. use the same
InternalPackedArray for both extras and natives). But this seems reasonable.

[Yang, 2015-10-14 13:33:38]

On 2015/10/13 22:08:07, domenic wrote:
> Open to alternate suggestions on how to approach this (e.g. use the same
> InternalPackedArray for both extras and natives). But this seems reasonable.

lgtm.

[domenic, 2015-10-14 15:52:03]

The CQ bit was checked by domenic@chromium.org

[commit-bot: I haz the power, 2015-10-14 15:52:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1401243003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1401243003/20001

[commit-bot: I haz the power, 2015-10-14 17:40:50]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-14 17:41:04]

Patchset 2 (id:??) landed as
https://crrev.com/8f8457d2a414b1cdad6dc3cecff062a8ff5649cb
Cr-Commit-Position: refs/heads/master@{#31272}