[builtins] Migrate String.fromCharCode to C++.

[builtins] Migrate String.fromCharCode to C++.

The previous JavaScript version created way too many ConsStrings for
longer strings, i.e. when using String.fromCharCode together with
Function.prototype.apply and arrays of char codes.

This version now always allocates sequential strings and therefore uses
way less memory when turning longer character sequences into strings,
and therefore fixes the memory regression on Google Maps.

BUG=chromium:609831
R=yangguo@chromium.org

Committed: https://crrev.com/cc71837fdae85a2b92db65d29146b2ab89ba77da
Cr-Commit-Position: refs/heads/master@{#36427}

[Benedikt Meurer, 2016-05-21 09:38:34]

Hey Yang,

Here's the fix for String.fromCharCode regression on Google Maps.
Please take a look.

Thanks,
Benedikt

[Yang, 2016-05-21 11:45:49]

lgtm. We still have the inlined fast path for the one argument case (at least in
crankshaft), right?

[Benedikt Meurer, 2016-05-21 16:52:25]

Yes, that's untouched. I also want to do a fast inline path for TurboFan, but
separate CL, since this one likely needs back-merging.

[Benedikt Meurer, 2016-05-21 16:56:29]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-05-21 16:56:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2004733002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2004733002/1

[commit-bot: I haz the power, 2016-05-21 16:58:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-21 17:00:09]

Description was changed from

==========
[builtins] Migrate String.fromCharCode to C++.

The previous JavaScript version created way too many ConsStrings for
longer strings, i.e. when using String.fromCharCode together with
Function.prototype.apply and arrays of char codes.

This version now always allocates sequential strings and therefore uses
way less memory when turning longer character sequences into strings,
and therefore fixes the memory regression on Google Maps.

BUG=chromium:609831
R=yangguo@chromium.org
==========

to

==========
[builtins] Migrate String.fromCharCode to C++.

The previous JavaScript version created way too many ConsStrings for
longer strings, i.e. when using String.fromCharCode together with
Function.prototype.apply and arrays of char codes.

This version now always allocates sequential strings and therefore uses
way less memory when turning longer character sequences into strings,
and therefore fixes the memory regression on Google Maps.

BUG=chromium:609831
R=yangguo@chromium.org

Committed: https://crrev.com/cc71837fdae85a2b92db65d29146b2ab89ba77da
Cr-Commit-Position: refs/heads/master@{#36427}
==========

[commit-bot: I haz the power, 2016-05-21 17:00:10]

Patchset 1 (id:??) landed as
https://crrev.com/cc71837fdae85a2b92db65d29146b2ab89ba77da
Cr-Commit-Position: refs/heads/master@{#36427}