Simplify/speedup collecting dictionary element keys

Simplify/speedup collecting dictionary element keys

BUG=

Committed: https://crrev.com/982efab91fee896077f8bd2317d7b2d1b6d49c41
Cr-Commit-Position: refs/heads/master@{#34779}

[Toon Verwaest, 2016-03-15 09:19:18]

verwaest@chromium.org changed reviewers:
+ cbruni@chromium.org

[Toon Verwaest, 2016-03-15 09:19:19]

ptal

[Camillo Bruni, 2016-03-15 09:20:14]

lgtm

[Toon Verwaest, 2016-03-15 09:55:13]

The CQ bit was checked by verwaest@chromium.org

[Toon Verwaest, 2016-03-15 09:55:13]

The patchset sent to the CQ was uploaded after l-g-t-m from cbruni@chromium.org
Link to the patchset: https://codereview.chromium.org/1792283007/#ps20001
(title: " ")

[commit-bot: I haz the power, 2016-03-15 09:55:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1792283007/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1792283007/20001

[commit-bot: I haz the power, 2016-03-15 10:04:11]

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

[commit-bot: I haz the power, 2016-03-15 10:04:12]

Try jobs failed on following builders:
  v8_win_rel_ng on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_rel_ng/builds/4357)

[Toon Verwaest, 2016-03-15 10:29:28]

The CQ bit was checked by verwaest@chromium.org

[Toon Verwaest, 2016-03-15 10:29:28]

The patchset sent to the CQ was uploaded after l-g-t-m from cbruni@chromium.org
Link to the patchset: https://codereview.chromium.org/1792283007/#ps40001
(title: "Rebase")

[commit-bot: I haz the power, 2016-03-15 10:29:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1792283007/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1792283007/40001

[commit-bot: I haz the power, 2016-03-15 10:52:13]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-03-15 10:52:35]

Description was changed from

==========
Simplify/speedup collecting dictionary element keys

BUG=
==========

to

==========
Simplify/speedup collecting dictionary element keys

BUG=

Committed: https://crrev.com/982efab91fee896077f8bd2317d7b2d1b6d49c41
Cr-Commit-Position: refs/heads/master@{#34779}
==========

[commit-bot: I haz the power, 2016-03-15 10:52:36]

Patchset 3 (id:??) landed as
https://crrev.com/982efab91fee896077f8bd2317d7b2d1b6d49c41
Cr-Commit-Position: refs/heads/master@{#34779}