Add enable_hangout_services_extension flag to GN build.

Add enable_hangout_services_extension flag to GN build.

This does not yet control anything, but is now hooked up to the C++ and grit defines as in GYP.

R=bemasc@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/2954bd38c7dfd9e5c36fae26ccaafb9088605bf8

[brettw, 2014-12-01 20:49:37]

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

[bemasc, 2014-12-01 20:56:43]

lgtm

[brettw, 2014-12-01 22:17:10]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2014-12-01 22:18:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/751613006/1

[commit-bot: I haz the power, 2014-12-01 22:18:09]

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

[commit-bot: I haz the power, 2014-12-01 22:18:10]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM 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.

[commit-bot: I haz the power, 2014-12-01 22:23:25]

Patchset 1 (id:??) landed as
https://crrev.com/2954bd38c7dfd9e5c36fae26ccaafb9088605bf8
Cr-Commit-Position: refs/heads/master@{#306270}

[brettw, 2014-12-01 22:23:38]

Committed patchset #1 (id:1) manually as
2954bd38c7dfd9e5c36fae26ccaafb9088605bf8 (presubmit successful).