Define WEBRTC_CHROMIUM_BUILD in libjingle.gyp.

Define WEBRTC_CHROMIUM_BUILD in libjingle.gyp.

Code under webrtc/ expects this to be defined when building against
Chromium. With talk/base having moved to webrtc/base, libjingle code
must adopt this expectation. This appears to be the most straightforward
way of adding this define.

In particular, this is now required to avoid redefinition errors after
the addition of CHECK macros to webrtc/base.

TESTED=local Linux build against the latest webrtc passes.

Committed: https://crrev.com/67fa5e94bdbd9eb7bce39c0cd6922321cf4998c9
Cr-Commit-Position: refs/heads/master@{#292676}

[ajm, 2014-08-29 01:08:14]

ajm@chromium.org changed reviewers:
+ hellner@chromium.org, sergeyu@chromium.org

[ajm, 2014-08-29 01:08:14]

Henrik: since you know the context.
Sergey: owner stamp.

[hellner1, 2014-08-29 15:56:36]

lgtm relevant standalone cl is
https://code.google.com/p/webrtc/source/detail?r=7004

[ajm, 2014-08-29 16:12:15]

Thanks. Sergey, could you give this an owner stamp?

[Sergey Ulanov, 2014-08-29 17:36:27]

lgtm

[ajm, 2014-08-29 17:44:20]

The CQ bit was checked by ajm@chromium.org

[commit-bot: I haz the power, 2014-08-29 17:46:05]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ajm@chromium.org/516143002/1

[commit-bot: I haz the power, 2014-08-29 19:03:04]

Committed patchset #1 (id:1) as 51326186c35a523a0ccc2efce3c1b83e885a3fcf

[commit-bot: I haz the power, 2014-09-10 03:10:19]

Patchset 1 (id:??) landed as
https://crrev.com/67fa5e94bdbd9eb7bce39c0cd6922321cf4998c9
Cr-Commit-Position: refs/heads/master@{#292676}