make v8_use_snapshot configurable in gn

make v8_use_snapshot configurable in gn

Changing this value is not guaranteed to work yet, but it needs to be
an arg in order to experiment with it.

Committed: https://crrev.com/d62efc128402520f23ef41e40d7ccf420f4d6e80
Cr-Commit-Position: refs/heads/master@{#31932}

[Mostyn Bramley-Moore, 2015-11-05 11:41:14]

The CQ bit was checked by mostynb@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2015-11-05 11:41:25]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1427343003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1427343003/1

[commit-bot: I haz the power, 2015-11-05 11:41:26]

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

[commit-bot: I haz the power, 2015-11-05 11:41:26]

Dry run: No L-G-T-M from a valid reviewer yet. Only full committers are
accepted.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Mostyn Bramley-Moore, 2015-11-05 11:43:02]

mostynb@opera.com changed reviewers:
+ jochen@chromium.org

[Mostyn Bramley-Moore, 2015-11-05 11:43:02]

@Jochen: can we start turning some of these v8 gn settings into args?  

This particular setting looks like it's relevant to other consumers of v8 also,
eg https://codereview.chromium.org/832413005

[jochen (gone - plz use gerrit), 2015-11-06 05:31:13]

jochen@chromium.org changed reviewers:
+ brettw@chromium.org

[jochen (gone - plz use gerrit), 2015-11-06 05:31:13]

+brettw for gn stuff

[brettw, 2015-11-10 20:48:42]

LGTM with comment addition.

https://codereview.chromium.org/1427343003/diff/1/BUILD.gn
File BUILD.gn (right):

https://codereview.chromium.org/1427343003/diff/1/BUILD.gn#newcode17
BUILD.gn:17: v8_use_snapshot = true
This should have some documentation about what a snapshot is and why you would
want to set (or unset) it.

[Mostyn Bramley-Moore, 2015-11-10 22:59:51]

@Jochen: how does this documentation of v8_use_snapshot look?

https://codereview.chromium.org/1427343003/diff/1/BUILD.gn
File BUILD.gn (right):

https://codereview.chromium.org/1427343003/diff/1/BUILD.gn#newcode17
BUILD.gn:17: v8_use_snapshot = true
On 2015/11/10 20:48:42, brettw wrote:
> This should have some documentation about what a snapshot is and why you would
> want to set (or unset) it.

Done.  Added the same documentation in build/features.gypi while I was at it.

[jochen (gone - plz use gerrit), 2015-11-10 23:02:44]

lgtm

[Mostyn Bramley-Moore, 2015-11-11 00:12:19]

The CQ bit was checked by mostynb@opera.com

[Mostyn Bramley-Moore, 2015-11-11 00:12:19]

The patchset sent to the CQ was uploaded after l-g-t-m from brettw@chromium.org
Link to the patchset: https://codereview.chromium.org/1427343003/#ps20001
(title: "document v8_use_snapshot")

[commit-bot: I haz the power, 2015-11-11 00:12:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1427343003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1427343003/20001

[commit-bot: I haz the power, 2015-11-11 01:09:12]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-11 01:09:24]

Patchset 2 (id:??) landed as
https://crrev.com/d62efc128402520f23ef41e40d7ccf420f4d6e80
Cr-Commit-Position: refs/heads/master@{#31932}