[flags] adding --trace_for_in_enumerate

[flags] adding --trace_for_in_enumerate

With the flag enables we print the keys found on each prototype and
the number of prototypes.

BUG=

Committed: https://crrev.com/62e9caf7184203ba5b280eb4b6876f22f0531aea
Cr-Commit-Position: refs/heads/master@{#34680}

[Camillo Bruni, 2016-03-08 18:48:33]

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

[Camillo Bruni, 2016-03-08 18:48:33]

PTAL

I used this a couple of times for tracing the key distribution on certain
websites, seems useful enough to add with a flag

[Toon Verwaest, 2016-03-09 19:19:30]

lgtm

[Camillo Bruni, 2016-03-10 14:37:01]

The CQ bit was checked by cbruni@chromium.org

[commit-bot: I haz the power, 2016-03-10 14:37:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1779523002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1779523002/1

[commit-bot: I haz the power, 2016-03-10 15:02:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-10 15:03:44]

Description was changed from

==========
[flags] adding --trace_for_in_enumerate

With the flag enables we print the keys found on each prototype and
the number of prototypes.

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

to

==========
[flags] adding --trace_for_in_enumerate

With the flag enables we print the keys found on each prototype and
the number of prototypes.

BUG=

Committed: https://crrev.com/62e9caf7184203ba5b280eb4b6876f22f0531aea
Cr-Commit-Position: refs/heads/master@{#34680}
==========

[commit-bot: I haz the power, 2016-03-10 15:03:45]

Patchset 1 (id:??) landed as
https://crrev.com/62e9caf7184203ba5b280eb4b6876f22f0531aea
Cr-Commit-Position: refs/heads/master@{#34680}