Improve iOS frame capture threading.

webrtc/base/objc/RTCDispatcher+Private.h

Index: webrtc/base/objc/RTCDispatcher+Private.h
diff --git a/webrtc/api/remoteaudiotrack.h b/webrtc/base/objc/RTCDispatcher+Private.h
similarity index 72%
copy from webrtc/api/remoteaudiotrack.h
copy to webrtc/base/objc/RTCDispatcher+Private.h
index 47de1b4dc8cd39ea52351e1502905487a0f3f3dd..2ef6cf1ef354d17e04f0571c13919517093c9830 100644
--- a/webrtc/api/remoteaudiotrack.h
+++ b/webrtc/base/objc/RTCDispatcher+Private.h
@@ -8,4 +8,10 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-// TODO(tommi): Delete this file when removed from build files in Chromium.
+#import "webrtc/base/objc/RTCDispatcher.h"
+
+@interface RTCDispatcher ()
+
++ (dispatch_queue_t)dispatchQueueForType:(RTCDispatcherQueueType)dispatchType;
+
+@end