gn: Reduce stack memory use while parsing.

gn: Reduce stack memory use while parsing.

BUG=641454
Committed: https://crrev.com/9e92b9d9ef75b26947a46ed3bc2735fddc888b3f
Cr-Commit-Position: refs/heads/master@{#415181}

[Nico, 2016-08-29 16:57:13]

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

[commit-bot: I haz the power, 2016-08-29 17:09:42]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-29 18:02:08]

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

[commit-bot: I haz the power, 2016-08-29 18:02:09]

Dry run: This issue passed the CQ dry run.

[Nico, 2016-08-29 18:05:48]

thakis@chromium.org changed reviewers:
+ brettw@chromium.org, scottmg@chromium.org

[Nico, 2016-08-29 18:05:48]

Not sure if this is a good change -- it's motivated by a fuzzer running out of
stack, and this doesn't fix that, it just makes it so that it takes a bit longer
until it happens. On the other hand, the code doesn't look worse with the
change, and using less stack is nice in the abstract. (In practice, it's just a
handful of bytes in common cases and doesn't seem to make a perf difference.)
Since I have the change locally, I figured I'd send it out and see what you
think.

Token is 48 bytes on 64-bit archs, references are 8 bytes. So it's at least 40
bytes stacks per recursion depth less, sometimes more (if a function has a local
Token in addition to the parameter).

[scottmg, 2016-08-29 18:20:31]

I can't recall any reason why I made it by value. Maybe it was "small" so it was
going to be "faster". Or "something".

lgtm

[Nico, 2016-08-29 19:49:24]

The CQ bit was checked by thakis@chromium.org

[commit-bot: I haz the power, 2016-08-29 20:25:28]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-30 05:50:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-30 05:52:11]

Description was changed from

==========
gn: Reduce stack memory use while parsing.

BUG=641454
==========

to

==========
gn: Reduce stack memory use while parsing.

BUG=641454

Committed: https://crrev.com/9e92b9d9ef75b26947a46ed3bc2735fddc888b3f
Cr-Commit-Position: refs/heads/master@{#415181}
==========

[commit-bot: I haz the power, 2016-08-30 05:52:11]

Patchset 1 (id:??) landed as
https://crrev.com/9e92b9d9ef75b26947a46ed3bc2735fddc888b3f
Cr-Commit-Position: refs/heads/master@{#415181}