Remove all the OS X 10.6 SDK forward declarations.

media/audio/mac/audio_output_mac.cc

Index: media/audio/mac/audio_output_mac.cc
diff --git a/media/audio/mac/audio_output_mac.cc b/media/audio/mac/audio_output_mac.cc
index ecfd0ad6b19afd012671e2addc8f655175f6e072..143d1084cce377bb3f837f4d77f178972b670e1d 100644
--- a/media/audio/mac/audio_output_mac.cc
+++ b/media/audio/mac/audio_output_mac.cc
@@ -38,13 +38,6 @@ struct AudioQueueUserData {
 // 6) The same thread that called stop will call Close() where we cleanup
 // and notifiy the audio manager, which likley will destroy this object.
 
-#if !defined(MAC_OS_X_VERSION_10_6) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_6
-enum {
-  kAudioQueueErr_EnqueueDuringReset = -66632
-};
-#endif
-
 PCMQueueOutAudioOutputStream::PCMQueueOutAudioOutputStream(
     AudioManagerMac* manager, const AudioParameters& params)
     : audio_queue_(NULL),