[es6] Introduce a dedicated JSIteratorResult type.

[es6] Introduce a dedicated JSIteratorResult type.

Use a single JSIteratorResult type for all implementation provided
iterator results (i.e. the String, Array and collection iterators,
and also for generators).  This removes one source of unnecessary
polymorphism in for-of loops.  It is accomplished by a new intrinsic
%_CreateIterResultObject() that should be used to create iterator
result objects from JavaScript builtins (there's a matching factory
method for C++ code).

Also restructure the %StringIteratorPrototype%.next() and
%ArrayIteratorPrototype%.next() functions to be a bit more friendly
to optimizing compilers.

R=ishell@chromium.org

Committed: https://crrev.com/72bc4b5c8a5c4279bcb8b340edbc8aa1c46d75a1
Cr-Commit-Position: refs/heads/master@{#30557}

[Benedikt Meurer, 2015-09-03 10:41:28]

Hey Igor,

This is a first step towards faster iterators for ES6 for-of loops.
With this new type we make sure that all iterator results we see
(coming from our internals and generators) have the same map.
Please take a look.

Thanks,
Benedikt

[Benedikt Meurer, 2015-09-03 11:27:32]

The CQ bit was checked by bmeurer@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-03 11:27:43]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1302173007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1302173007/1

[commit-bot: I haz the power, 2015-09-03 11:29:26]

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

[commit-bot: I haz the power, 2015-09-03 11:29:26]

Dry run: This issue passed the CQ dry run.

[Jarin, 2015-09-03 12:05:34]

jarin@chromium.org changed reviewers:
+ jarin@chromium.org

[Jarin, 2015-09-03 12:05:35]

lgtm

[Benedikt Meurer, 2015-09-03 12:05:47]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-09-03 12:05:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1302173007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1302173007/1

[commit-bot: I haz the power, 2015-09-03 12:09:17]

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

[commit-bot: I haz the power, 2015-09-03 12:09:18]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/5509)

[Michael Starzinger, 2015-09-03 12:13:39]

mstarzinger@chromium.org changed reviewers:
+ mstarzinger@chromium.org

[Michael Starzinger, 2015-09-03 12:13:39]

LGTM (rubber-stamp for "heap", didn't look at the rest at all).

[Benedikt Meurer, 2015-09-03 12:13:50]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-09-03 12:14:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1302173007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1302173007/1

[commit-bot: I haz the power, 2015-09-03 12:16:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-03 12:16:35]

Patchset 1 (id:??) landed as
https://crrev.com/72bc4b5c8a5c4279bcb8b340edbc8aa1c46d75a1
Cr-Commit-Position: refs/heads/master@{#30557}