Cast: IPC glue between cast library transport and encoders.

media/cast/cast_sender.gyp

Index: media/cast/cast_sender.gyp
diff --git a/media/cast/cast_sender.gyp b/media/cast/cast_sender.gyp
index 5738106aa9f860cfbda689bde637bf823648cbee..7a29accbd8ae0a85aae13e2d402c9515252c5295 100644
--- a/media/cast/cast_sender.gyp
+++ b/media/cast/cast_sender.gyp
@@ -27,6 +27,9 @@
         'rtcp/rtcp.gyp:cast_rtcp',
         'video_sender',
       ], # dependencies
+      'defines' : [
+        'MEDIA_IMPLEMENTATION',
+      ],
     },
   ],
 }