Add webrtcmediaengine.* to libjingle.gyp

Pending move of CreateWebRtcMediaEngine() to webrtcmediaengine.cc.

BUG=webrtc:1788
R=ronghuawu@chromium.org

Review URL: https://codereview.chromium.org/322433007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275502 0039d316-1c4b-4281-b951-d872f2087c98

third_party/libjingle/libjingle.gyp

@@ -586,6 +586,8 @@
           'target_name': 'libpeerconnection',
           'type': '<(libpeer_target_type)',
           'sources': [
+            '<(libjingle_source)/talk/media/webrtc/webrtcmediaengine.cc',
+            '<(libjingle_source)/talk/media/webrtc/webrtcmediaengine.h',
             '<(libjingle_source)/talk/media/webrtc/webrtcvideoengine.cc',
             '<(libjingle_source)/talk/media/webrtc/webrtcvideoengine.h',
             '<(libjingle_source)/talk/media/webrtc/webrtcvideoengine2.cc',