Optionally use new GN optimization config.

Optionally use new GN optimization config.

The GN default optimization flag is changing from being specific to the
debug/release status of the build to always being "default_optimization" so
it's easier to override without being conditional on the exact setup in
BUILDCONFIG.gn. See https://codereview.chromium.org/1324623005/

Since V8 is DEPS-ed in, it will need to support both modes to allow a landing.
This patch uses a temporary transitional flag I added to BUILDCONFIG to
indicate which variant should be used. After the patch is landed, we can remove
the new conditions and just remove default_optimization.

Committed: https://crrev.com/ea8cfa929fcd90975039cb037e7547bf75d7aec9
Cr-Commit-Position: refs/heads/master@{#30703}

[brettw, 2015-09-10 17:54:13]

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

[brettw, 2015-09-10 17:54:13]

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

[brettw, 2015-09-10 17:54:13]

Please puch CQ button if it looks good. Thanks!

[brettw, 2015-09-10 17:54:13]

Please puch CQ button if it looks good. Thanks!

[jochen (gone - plz use gerrit), 2015-09-11 17:34:02]

The CQ bit was checked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-09-11 17:34:02]

lgtm

[commit-bot: I haz the power, 2015-09-11 17:34:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1333963002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1333963002/1

[commit-bot: I haz the power, 2015-09-11 18:28:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-11 18:28:35]

Patchset 1 (id:??) landed as
https://crrev.com/ea8cfa929fcd90975039cb037e7547bf75d7aec9
Cr-Commit-Position: refs/heads/master@{#30703}