Correct property descriptors on GeneratorPrototype

Correct property descriptors on GeneratorPrototype

The ES6 specification does not explicitly state the attributes for the
'next' and 'throw' property descriptors, so their values are defined by
Section 17 [1]:

> Every other data property described in clauses 18 through 26 and in
> Annex B.2 has the attributes
> { [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }
> unless otherwise specified.

[1]
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-standard-built-in-objects

BUG=v8:3986
LOG=N
R=wingo,arv

Committed: https://crrev.com/0a4881600d0a7162038f54969ba521c58f4e6e4d
Cr-Commit-Position: refs/heads/master@{#27770}

[mike3, 2015-04-02 19:11:34]

mike@mikepennisi.com changed reviewers:
+ arv@chromium.org

[mike3, 2015-04-02 19:11:35]

Hi Erik: could you please take a look?

Also, I referenced the V8 bug ID in the commit message, but the link generated
by the web interface is to the (completely unrelated) Chromium bug with that ID.
If I can/should correct that, please let me know how

[arv (Not doing code reviews), 2015-04-02 19:20:22]

On 2015/04/02 19:11:35, mike3 wrote:
> Hi Erik: could you please take a look?
> 
> Also, I referenced the V8 bug ID in the commit message, but the link generated
> by the web interface is to the (completely unrelated) Chromium bug with that
ID.
> If I can/should correct that, please let me know how

Prefix the bug number with v8: and the link will work. (I'm updating it for you
now).

[arv (Not doing code reviews), 2015-04-02 19:20:38]

arv@chromium.org changed reviewers:
+ wingo@igalia.com

[arv (Not doing code reviews), 2015-04-02 19:21:52]

LGTM

[wingo, 2015-04-10 14:30:46]

On 2015/04/02 19:21:52, arv wrote:
> LGTM

lgtm as well, adding to cq

[wingo (chromium), 2015-04-10 14:31:17]

The CQ bit was checked by wingo@chromium.org

[commit-bot: I haz the power, 2015-04-10 14:31:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051363003/1

[commit-bot: I haz the power, 2015-04-10 14:50:38]

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

[commit-bot: I haz the power, 2015-04-10 14:50:39]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/1898)

[mike3, 2015-04-11 20:50:06]

The CQ bit was checked by mike@mikepennisi.com

[commit-bot: I haz the power, 2015-04-11 20:50:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051363003/1

[commit-bot: I haz the power, 2015-04-11 21:14:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-11 21:14:38]

Patchset 1 (id:??) landed as
https://crrev.com/0a4881600d0a7162038f54969ba521c58f4e6e4d
Cr-Commit-Position: refs/heads/master@{#27770}