Revert 226264 "Be able to build cast_unittest and related target..."

trunk/src/media/cast/audio_receiver/audio_receiver.cc

Index: trunk/src/media/cast/audio_receiver/audio_receiver.cc
===================================================================
--- trunk/src/media/cast/audio_receiver/audio_receiver.cc	(revision 226266)
+++ trunk/src/media/cast/audio_receiver/audio_receiver.cc	(working copy)
@@ -71,6 +71,10 @@
     audio_receiver_->CastFeedback(cast_message);
   }
 
+  virtual void RequestKeyFrame() OVERRIDE {
+    DCHECK(false) << "Invalid callback";
+  }
+
  private:
   AudioReceiver* audio_receiver_;
 };